code: function splitOnFirst(str, splitter, callback) {
          var parts = str.split(splitter);
          var first = parts.shift();
          return callback(first, parts.join(splitter));
      }
docs: splits a string on the first occurrence of 'splitter' and calls back with the two entries.
  @param {string} str
  @param {string} splitter
  @param {function} callback
  @return *