Build: Add grunt-cli to devDependencies, don't install it globally

This makes it possible to use Grunt without installing grunt-cli globally
which makes the whole process more resilient.

Ref gh-1706

.travis.yml

@@ -3,5 +3,3 @@ dist: trusty
 language: node_js
 node_js:
   - "0.12"
-before_script:
-  - npm install -g grunt-cli

package.json

@@ -55,6 +55,7 @@
 		"commitplease": "2.3.0",
 		"grunt": "0.4.5",
 		"grunt-bowercopy": "1.2.4",
+		"grunt-cli": "0.1.13",
 		"grunt-compare-size": "0.4.0",
 		"grunt-contrib-concat": "0.5.1",
 		"grunt-contrib-csslint": "0.5.0",