Use -W when building docs (make warnings errors).

Fix a couple of warnings that sphinx was complaining about.
Move pych --testing call to test_python.bash script.

It should work now, since the test_python.bash script correctly configures the environment.
Use portable open command in top level makefile.
Install pyChapel from repo, instead of pypi for travis testing.
Merge pull request #1 from thomasvandoren/fix-build-breakages

Fix build breakages and a couple other cleanup items.