function createMarkup(obj) {
  var keys = Object.keys(obj);
  if (!keys.length) return '';
  var i,
      len = keys.length;
  var result = '';

  for (i = 0; i < len; i++) {
    var key = keys[i];
    var val = obj[key];
    result += hyphenate(key) + ':' + addPx(key, val) + ';';
  }

  return result;
}
Convert a JS object to CSS string. Similar to React's output of CSS.
@param obj
@returns {string}