Adding JUnit support.

[cpkleynhans]

Changes:

• Adds a waf task all, which runs everything except for configure and deps
• Adds a waf task deps, which downloads dependencies into deps directory
• Adds a waf task test, which runs the KodKod JUnit TestSuite
• Adds sample JUnit test suites and test
• Updates travis config to download dependencies and run tests
• Adds a gitignore

Reviewers: @AtulanZaman @mhyee @joseph2625

[mhyee]

Two minor points: (currently) unnecessary import and trailing whitespace in various places.

We can ignore the minor points for now.

I also have two major comments:

• Do we want to download the JUnit dependencies? We've had this discussion before; it's annoying to depend on something external, but we also don't want to include them in the repo. Either way, we might want to be consistent with waf. So either download everything or include everything.
• This looks like it'll merge fine into master, but will it merge cleanly into the overflows? This probably isn't a huge issue for us, but it'd be nice to confirm that our tests will merge in.

[cpkleynhans]

I've fixed your minor points.

In order for us to download waf we would need to add another script or something to download dependencies. This seems a bit excessive so for waf we have two decisions really, include it in the repo, or assume the user has it installed already. I prefer including it in the repo.

Overflow appears to be using an older version of junit, so we would need to update the tests to the latest version. The tests are also organized in a slightly different way but it shouldn't be hard to adjust them.

[mhyee]

OK, looks good then.

[joseph39]

looks good!

[cpkleynhans]

We discussed offline that we should move test building into its own task. I'll be pushing a commit with this change shortly.