Parallel petclaw tests in Travis
Clean up 3D acoustics test
Improve nosetest output (use test descriptions)
Serialize extension module auto-build in Rossby
Merge remote-tracking branch 'origin/master' into ahmadia/travis_test_petclaw
Make it possible to automatically build SW-sphere modules from same
directory.

Also, fail if one process returns None for initial data but
not for final data in 3D acoustics test.
Merge pull request #398 from clawpack/ahmadia/travis_test_petclaw

Parallel petclaw tests in Travis