chore(.travis.yml): fix for running tests with grunt

.travis.yml

@@ -6,6 +6,7 @@ node_js:
 before_install:
   - '[ "${TRAVIS_NODE_VERSION}" != "0.8" ] || npm install -g npm@1.4.28'
   - npm install -g npm@latest
+  - npm install -g grunt-cli
 
 #travis build  speed up
 sudo: false