code: function getHelpers(options) {
    const helpers = {};
    return new Promise((resolve, reject) => {
      if (isGlob(options.helpers)) {
        getFiles(options.helpers).then(helperPaths => {
          helperPaths.forEach(hPath => {
            helpers[keyname(hPath)] = require(hPath);
          });
          resolve(helpers);
        });
      } else {
        resolve(options.helpers);
      }
    });
  }
docs: Register helpers on Handlebars. Helpers (options.helpers) can be provided as
  either:
  - a glob. Files matching glob will each be require'd and registered on
  Handlebars (one helper per module)
  - an object. Properties are helper names/keys, values should be helper
  functions.
  
  @param {Object} options with `helpers` property
  @return {Promise} resolving to the helpers that have been registered