常用文件的后缀，上传时的文件类型
记录下来备用：
'unkown' => 'application/octet-stream', 'acx' => 'application/internet-property-stream', 'ai' => 'application/postscript', 'aif' => 'audio/x-aiff', 'aifc' => 'audio/x-aiff', 'aiff' => 'audio/x-aiff', 'asp' => 'text/plain', 'aspx' => 'text/plain', 'asf' => 'video/x-ms-asf', 'asr' => 'video/x-ms-asf', 'asx' => 'video/x-ms-asf', 'au' => 'audio/basic', 'avi' => 'video/x-msvideo', 'axs' => 'application/olescript', 'bas' => 'text/plain', 'bcpio' => 'application/x-bcpio', 'bin' => 'application/octet-stream', 'bmp' => 'image/bmp', 'c' => 'text/plain', 'cat' => 'application/vnd.ms-pkiseccat', 'cdf' => 'application/x-cdf', 'cer' => 'application/x-x509-ca-cert', 'class' => 'application/octet-stream', 'clp' => 'application/x-msclip', 'cmx' => 'image/x-cmx', 'cod' => 'image/cis-cod', 'cpio' => 'application/x-cpio', 'crd' => 'application/x-mscardfile', 'crl' => 'application/pkix-crl', 'crt' => 'application/x-x509-ca-cert', 'csh' => 'application/x-csh', 'css' => 'text/css', 'dcr' => 'application/x-director', 'der' => 'application/x-x509-ca-cert', 'dir' => 'application/x-director', 'dll' => 'application/x-msdownload', 'dms' => 'application/octet-stream', 'doc' => 'application/msword', 'docx' => 'application/msword', 'dot' => 'application/msword', 'dvi' => 'application/x-dvi', 'dxr' => 'application/x-director', 'eps' => 'application/postscript', 'etx' => 'text/x-setext', 'evy' => 'application/envoy', 'exe' => 'application/octet-stream', 'fif' => 'application/fractals', 'flr' => 'x-world/x-vrml', 'flv' => 'video/x-flv', 'gif' => 'image/gif', 'gtar' => 'application/x-gtar', 'gz' => 'application/x-gzip', 'h' => 'text/plain', 'hdf' => 'application/x-hdf', 'hlp' => 'application/winhlp', 'hqx' => 'application/mac-binhex40', 'hta' => 'application/hta', 'htc' => 'text/x-component', 'htm' => 'text/html', 'html' => 'text/html', 'shtml' => 'text/html', 'htt' => 'text/webviewhtml', 'ico' => 'image/x-icon', 'ief' => 'image/ief', 'iii' => 'application/x-iphone', 'ins' => 'application/x-internet-signup', 'isp' => 'application/x-internet-signup', 'jfif' => 'image/pipeg', 'jpe' => 'image/jpeg', 'jpeg' => 'image/jpeg', 'jpg' => 'image/jpeg', 'js' => 'application/x-javascript', 'latex' => 'application/x-latex', 'lha' => 'application/octet-stream', 'lsf' => 'video/x-la-asf', 'lsx' => 'video/x-la-asf', 'lzh' => 'application/octet-stream', 'm13' => 'application/x-msmediaview', 'm14' => 'application/x-msmediaview', 'm3u' => 'audio/x-mpegurl', 'man' => 'application/x-troff-man', 'mdb' => 'application/x-msaccess', 'me' => 'application/x-troff-me', 'mht' => 'message/rfc822', 'mhtml' => 'message/rfc822', 'mid' => 'audio/mid', 'mny' => 'application/x-msmoney', 'mov' => 'video/quicktime', 'movie' => 'video/x-sgi-movie', 'mp2' => 'video/mpeg', 'mp3' => 'audio/mpeg', 'mpa' => 'video/mpeg', 'mpe' => 'video/mpeg', 'mpeg' => 'video/mpeg', 'mpg' => 'video/mpeg', 'mpp' => 'application/vnd.ms-project', 'mpv2' => 'video/mpeg', 'ms' => 'application/x-troff-ms', 'mvb' => 'application/x-msmediaview', 'nws' => 'message/rfc822', 'oda' => 'application/oda', 'p10' => 'application/pkcs10', 'p12' => 'application/x-pkcs12', 'p7b' => 'application/x-pkcs7-certificates', 'p7c' => 'application/x-pkcs7-mime', 'p7m' => 'application/x-pkcs7-mime', 'p7r' => 'application/x-pkcs7-certreqresp', 'p7s' => 'application/x-pkcs7-signature', 'pbm' => 'image/x-portable-bitmap', 'pdf' => 'application/pdf', 'pfx' => 'application/x-pkcs12', 'pgm' => 'image/x-portable-graymap', 'pko' => 'application/ynd.ms-pkipko', 'pma' => 'application/x-perfmon', 'pmc' => 'application/x-perfmon', 'pml' => 'application/x-perfmon', 'pmr' => 'application/x-perfmon', 'pmw' => 'application/x-perfmon', 'png' => 'image/png', 'pnm' => 'image/x-portable-anymap', 'pot,' => 'application/vnd.ms-powerpoint', 'ppm' => 'image/x-portable-pixmap', 'pps' => 'application/vnd.ms-powerpoint', 'ppt' => 'application/vnd.ms-powerpoint', 'pptx' => 'application/vnd.ms-powerpoint', 'prf' => 'application/pics-rules', 'ps' => 'application/postscript', 'pub' => 'application/x-mspublisher', 'qt' => 'video/quicktime', 'ra' => 'audio/x-pn-realaudio', 'ram' => 'audio/x-pn-realaudio', 'ras' => 'image/x-cmu-raster', 'rgb' => 'image/x-rgb', 'rmi' => 'audio/mid', 'roff' => 'application/x-troff', 'rtf' => 'application/rtf', 'rtx' => 'text/richtext', 'scd' => 'application/x-msschedule', 'sct' => 'text/scriptlet', 'setpay' => 'application/set-payment-initiation', 'setreg' => 'application/set-registration-initiation', 'sh' => 'application/x-sh', 'shar' => 'application/x-shar', 'sit' => 'application/x-stuffit', 'snd' => 'audio/basic', 'spc' => 'application/x-pkcs7-certificates', 'spl' => 'application/futuresplash', 'src' => 'application/x-wais-source', 'sst' => 'application/vnd.ms-pkicertstore', 'stl' => 'application/vnd.ms-pkistl', 'stm' => 'text/html', 'svg' => 'image/svg+xml', 'sv4cpio' => 'application/x-sv4cpio', 'sv4crc' => 'application/x-sv4crc', 'swf' => 'application/x-shockwave-flash', 't' => 'application/x-troff', 'tar' => 'application/x-tar', 'tcl' => 'application/x-tcl', 'tex' => 'application/x-tex', 'texi' => 'application/x-texinfo', 'texinfo' => 'application/x-texinfo', 'tgz' => 'application/x-compressed', 'tif' => 'image/tiff', 'tiff' => 'image/tiff', 'tr' => 'application/x-troff', 'trm' => 'application/x-msterminal', 'tsv' => 'text/tab-separated-values', 'txt' => 'text/plain', 'uls' => 'text/iuls', 'ustar' => 'application/x-ustar', 'vcf' => 'text/x-vcard', 'vrml' => 'x-world/x-vrml', 'wav' => 'audio/x-wav', 'wcm' => 'application/vnd.ms-works', 'wdb' => 'application/vnd.ms-works', 'wks' => 'application/vnd.ms-works', 'wmf' => 'application/x-msmetafile', 'wmv' => 'video/x-ms-wmv', 'wps' => 'application/vnd.ms-works', 'wri' => 'application/x-mswrite', 'wrl' => 'x-world/x-vrml', 'wrz' => 'x-world/x-vrml', 'xaf' => 'x-world/x-vrml', 'xbm' => 'image/x-xbitmap', 'xla' => 'application/vnd.ms-excel', 'xlc' => 'application/vnd.ms-excel', 'xlm' => 'application/vnd.ms-excel', 'xls' => 'application/vnd.ms-excel', 'xlsx' => 'application/vnd.ms-excel', 'xlt' => 'application/vnd.ms-excel', 'xlw' => 'application/vnd.ms-excel', 'xof' => 'x-world/x-vrml', 'xpm' => 'image/x-xpixmap', 'xwd' => 'image/x-xwindowdump', 'z' => 'application/x-compress', 'zip' => 'application/zip', 'rar' => 'application/zip', 'php' => 'text/x-php',