chore(bower): write grunt task for running bower

lib/grunt/plugins.js

@@ -1,3 +1,4 @@
+var bower = require('bower');
 var util = require('./utils.js');
 var spawn = require('child_process').spawn;
 
@@ -63,4 +64,15 @@ module.exports = function(grunt) {
   grunt.registerTask('collect-errors', 'Combine stripped error files', function () {
     util.collectErrors();
   });
+
+  grunt.registerTask('bower', 'Install Bower packages.', function () {
+    var done = this.async();
+
+    bower.commands.install()
+      .on('log', function (result) {
+        grunt.log.ok('bower: ' + result.id + ' ' + result.data.endpoint.name);
+      })
+      .on('error', grunt.fail.warn.bind(grunt.fail))
+      .on('end', done);
+  });
 };