code: function getFileMIME(file) {
    var idx = file.lastIndexOf('.')
    var ext = idx > -1 ? file.slice(idx) : null
    if (ext) ext = ext.toLowerCase().substring(1)
    return MIMES[ext] || MIMES.txt
  }
docs: get MIME by file name
  
  @param  {String} file
  @return {String}