Simple, AMD-like module definition. The module will be added into
<code>emmet</code> object and will be available via
<code>emmet.require(name)</code> or <code>emmet[name]</code>
@param {String} name
@param {Function} factory
@memberOf emmet
function(name, factory) {
			// do not let redefine existing properties
			if (!(name in modules)) {
				modules[name] = _.isFunction(factory) 
					? this.exec(factory)
					: factory;
			}
		}