add grunt eslint

.travis.yml

@@ -1,6 +1,16 @@
 language: node_js
 node_js:
     - "0.10"
+
+install:
+  - npm install
+
+before_script:
+  - npm install -g grunt-cli
+
+script:
+  - grunt eslint
+
 branches:
   only:
     - gh-page