Travis-CI integration

This adds .travis.yml and puts build and test status badge to README.md

Before merging this pull request, you should:

1. Sign in with your github credentials at https://travis-ci.org,
2. Enable Travis-CI service hook for kylelutz/compute repository at https://travis-ci.org/profile.

Also see http://about.travis-ci.org/docs/user/getting-started.