travis: no support for node < 0.10, no support for node >= 0.11

For node < 0.10, some dependencies cannot be solved. We really don't
care. For node >= 0.11, it seems that there are problems with sqlite3
extension. Didn't dig much, but may be related:
 TryGhost/node-sqlite3#184

Author: vincentbernat

.travis.yml

@@ -1,8 +1,5 @@
 language: node_js
 node_js:
-  - "0.11"
   - "0.10"
-  - "0.8"
-  - "0.6"
 before_install:
   - "npm install -g grunt-cli bower"