fix(travis): install sass gem if sass is enabled

Author: meeDamian

Diff for: app/templates/.travis.yml

@@ -1,8 +1,9 @@
 language: node_js
 node_js:
-  - '0.8'
   - '0.10'
+  - '0.11'
 before_script:
-  - 'npm install -g bower grunt-cli'
-  - 'bower install'
+  - npm install -g bower grunt-cli<% if (filters.sass) { %>
+  - gem install sass<% } %>
+  - bower install
 services: mongodb