[testing] add build caching

.travis.yml

@@ -2,15 +2,19 @@ language: node_js
 node_js:
 - '0.10'
 install:
-- npm install -g grunt-cli bower
+- npm install grunt-cli bower
 - npm install
-- bower install
 script:
 - npm test
+sudo: false
+cache:
+  directories:
+  - esvm
+  - node_modules
+  - src/kibana/bower_components
 notifications:
   email:
   - rashid.khan@elastic.co
-  - spencer.alger@elastic.co
   hipchat:
     rooms:
       secure: UKrVR+5KztHarodQruQe97UJfwftutD6RNdXlVkr+oIr2GqccisDIIN9pAzS/kxl+eAnP1uT6VHzc9YI/jgbrmiSkz3DHViw+MwDwY2aIDgI8aHEbd/4B2ihtb15+OYTVbb+lytyz4+W8A8hSmbkTR/P/uFIJ+EYcBeYZfw1elo=

package.json

@@ -32,6 +32,7 @@
     "test": "grunt test",
     "start": "node ./src/server/bin/kibana.js",
     "server": "node ./src/server/bin/kibana.js",
+    "postinstall": "bower install",
     "precommit": "grunt lintStagedFiles"
   },
   "repository": {