Node 0.8 was stalling travis builds. Updated travis.yml to remove Node 0...

Node 0.8 was stalling travis builds. Updated travis.yml to remove Node 0.8 build environment.
- Erring log: https://s3.amazonaws.com/archive.travis-ci.org/jobs/34187132/log.txt
- Example of erring job: https://travis-ci.org/fusioncharts/redraphael/jobs/34187132

Seems like the issue lies with lack of support for grunt with this version of NodeJS. The log shows:
```terminal
Error: No compatible version found: grunt@'^0.4.2'
```

PS: Also added build trigger for commit to `develop` branch.