function getGithubUrl(type, gh) {
  var url = [gh.host, 'repos', gh.username, gh.repo, 'contents', type + '?ref=' + gh.branch];
  if (gh.prefix) url.splice(5, 0, gh.prefix);
  return url.join('/');
}
Get Github URL based on configuration.
@function
@param {string} type - Type of file.
@returns {string} GIthub URL