text: var request = require("request");
  var toMarkdown = require("to-markdown").toMarkdown;
  
  
  // Determine if an particular transform exists.
  // Synchronous code, raises exception if it does not exist.
  exports.xformExists = function(xform) {
      try {
          xform = require("./xforms/" + xform);
          return true;
      } catch(e) {
          return false;
      }
  };
  
  
  exports.fetch = function(url, xform, callback) {
      var xformFn = require("./xforms/" + xform);
      request(url, function(err, res, body) {
          callback(err, toMarkdown(xformFn(body)));
      });
  };
  