code: function buildHeaders(file) {
      var mimeType, charset, headers;
      mimeType = mime.lookup(file);
      charset = mime.charsets.lookup(mimeType);
      headers = { 'Content-Type': mimeType };
      if (charset) headers.charset = charset;
      return headers;
  }
docs: ### buildHeaders
  
  Formats the response headers looking up the mime type of the file
  
  @param {string} file The name of the file (containing extension) that
  that will be sent to a client
  
  @return {object} headers The headers with the added 'Content-Type' property