add back pluginLoader
add back pluginLoader

systemjs/builder,whitneyit/builder,jrauschenbusch/builder,jrauschenbusch/builder,lookfirst/builder,alexisvincent/builder,buddhike/builder,alexisvincent/builder,systemjs/builder,lookfirst/builder,jrauschenbusch/builder,douglasduteil/builder,alexisvincent/builder,systemjs/builder,whitneyit/builder,buddhike/builder,douglasduteil/builder