Rename src/eng --> src/renderers

A renderer is a thing that renders or "paints" an arbitrary format using
a templating engine like Handlebars or Underscore. A generator is a
thing responsible for generating a given output format like HTML or MS
Word.

src/renderers/handlebars-helpers.js

@@ -0,0 +1,25 @@
+/**
+Template helper definitions for Handlebars.
+@license MIT. Copyright (c) 2015 James Devlin / FluentDesk.
+@module handlebars-helpers.js
+*/
+
+
+(function() {
+
+  var HANDLEBARS = require('handlebars')
+  , _ = require('underscore')
+  , helpers = require('./generic-helpers');
+
+  /**
+  Register useful Handlebars helpers.
+  @method registerHelpers
+  */
+  module.exports = function( theme ) {
+
+    helpers.theme = theme;
+    HANDLEBARS.registerHelper( helpers );
+
+  };
+
+}());