Use app.bowerDirectory instead of hardcoded bower_components

Author: soulim

Brocfile.js

@@ -18,11 +18,11 @@ var app = new EmberAddon();
 // please specify an object with the list of modules as keys
 // along with the exports of each module as its value.
 
-app.import('bower_components/bootstrap/dist/css/bootstrap.css');
-app.import('bower_components/bootstrap/dist/css/bootstrap.css.map', {
+app.import(app.bowerDirectory + '/bootstrap/dist/css/bootstrap.css');
+app.import(app.bowerDirectory + '/bootstrap/dist/css/bootstrap.css.map', {
   destDir: 'assets'
 });
 
-app.import('bower_components/bootstrap-datepicker/js/locales/bootstrap-datepicker.de.js');
+app.import(app.bowerDirectory + '/bootstrap-datepicker/js/locales/bootstrap-datepicker.de.js');
 
 module.exports = app.toTree();