chore(index): expose the Configuration class

webpack projects use this class to switch options on and off based on the environment

lib/index.js

@@ -6,3 +6,4 @@ exports.UI = require('./ui').UI;
 exports.Project = require('./project').Project;
 exports.ProjectItem = require('./project-item').ProjectItem;
 exports.build = require('./build');
+exports.Configuration = require('./configuration').Configuration;