code: function stripHeaderWhitespace (h){
      var n = {};
      var keys = Object.keys(h);
      keys.forEach(function(k){
          n[k] = h[k].replace(/,[ ]*/g, ',');
      });
      return n;
  }
docs: Private API:
  removes whitespace after commas (for headers),
  so "alligators, hippos" -> "alligators,hippos"
  @param {Object} h A set of headers, either expected or actual
  @return {Object} A set of headers with whitespace removed