Upgrade (explicitly) grunt

They deprecated the use of some packaged modules and suggest using those modules
directly. http://gruntjs.com/blog/2013-11-21-grunt-0.4.2-released

Lodash was the only use we had.

grunt/config/browserify.js

@@ -7,6 +7,7 @@ var envify = require('envify/custom');
 var grunt = require('grunt');
 var UglifyJS = require('uglify-js');
 var uglifyify = require('uglifyify');
+var _ = require('lodash');
 
 var SIMPLE_TEMPLATE =
 '/**\n\
@@ -65,7 +66,7 @@ var basic = {
   after: [simpleBannerify]
 };
 
-var min = grunt.util._.merge({}, basic, {
+var min = _.merge({}, basic, {
   outfile: './build/react.min.js',
   debug: false,
   transforms: [envify({NODE_ENV: 'production'}), uglifyify],
@@ -94,7 +95,7 @@ var addons = {
   after: [simpleBannerify]
 };
 
-var addonsMin = grunt.util._.merge({}, addons, {
+var addonsMin = _.merge({}, addons, {
   outfile: './build/react-with-addons.min.js',
   debug: false,
   transforms: [envify({NODE_ENV: 'production'}), uglifyify],

package.json

@@ -43,7 +43,7 @@
     "coverify": "~1.0.4",
     "envify": "~1.0.1",
     "es5-shim": "~2.3.0",
-    "grunt": "~0.4.1",
+    "grunt": "~0.4.2",
     "grunt-cli": "~0.1.9",
     "grunt-compare-size": "~0.4.0",
     "grunt-complexity": "~0.1.3",
@@ -54,6 +54,7 @@
     "grunt-contrib-jshint": "~0.8.0",
     "gzip-js": "~0.3.2",
     "jasmine-tapreporter": "~0.2.2",
+    "lodash": "~2.4.1",
     "microtime": "~0.5.1",
     "optimist": "~0.6.0",
     "phantomjs": "~1.9",