Workspace-level tests

[mikepurvis]

Related to #240, this package really needs some more intense workspace-level integration testing. One road forward on this could be to beef up the existing toy test workspace.

Unfortunately, several of the behaviours which matter the most come down to how packages like catkin itself, genmsg, etc. interact with each other, so it seems like it's going to be a bit of a mess basically re-implementing those behaviours inside test workspaces to test them.

I'm wondering about setting up another kind of test regime, which actually downloads sources for some of these external packages, and then exercises the different build configurations (devel, isolated devel, install, isolated install). This could be integrated with the existing nosetests, or left as a separate framework (for example, to be executed under travis, etc).

[jbohren]

My standing PR #196 cleans up and adds a ton of self-contained tests. I think you're right that it needs some real-world tests, too. Take a look what I already have here: https://github.com/jbohren-forks/catkin_tools/tree/clean-pkgs/tests/system/resources/catkin_pkgs

[jbohren]

A ton of workspace-level tests have been added with the pre-0.4.0 PRs, so I'm going to move this to the 1.0.0 milestone. We should look at doing some real coverage as well, and we can always have more tests.