update travis test environments

In order to continue development it might be good to update the travis test environments. Also there is no point in testing on the v0.9 release anymore.

Note: at least one test case is failing when running node v0.10 or v0.11. But that is another issue.
> FAILURES: Undone tests (or their setups/teardowns): 
> \- Secure connection - STARTTLS on secure server fails
> To fix this, make sure all tests call test.done()

* Remove old development branch v0.9
* Add latest stable version v0.10
* Add latest development branch v0.11