update travis file to be more explicit

.travis.yml

@@ -1,8 +1,18 @@
 language: node_js
 node_js:
-  - 0.10
+    - "0.10"
 
-before_script:
-  - npm install -g grunt-cli
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start
+branches:
+    only:
+        - master
+        - dev
+
+install:
+    - npm install -g grunt-cli
+    - export DISPLAY=:99.0
+    - sh -e /etc/init.d/xvfb start
+    - npm install
+
+script:
+    - grunt build
+    - grunt travis