add travis.yml

@jzoldak @benpatterson @cgoldberg 


See this PR for test results: https://github.com/clytwynec/harprofiler/pull/1
nitpick:
I think calling this in a sub-shell with deactivate the virtualenv.. so you'd have to reactivate it again after bootstrapping to run inside the virtualenv.  if you replace `bash install-bmp.sh` with `source install-bmp.sh`, it will inherit the activated virtualenv... so to bootstrap into an activated virtualenv, you can just:
$ source dev-bootstrap.py