Roll-out CI for Recaf

[charlesdaniels]

Recaf should have some sort of CI to:

• Ensure every commit compiles.
• Ensure documentation is build for every commit.
• Monitor CheckStyle/FindBugs issue count for every commit.
• Make build artifacts (jarfile, docs) are available for download.

I suggets investigating Travis CI as it is free for open source projects to use.

[Col-E]

Started as of https://github.com/Col-E/Recaf/commit/271c494cc6870a985d37af9116df657dd021369f

• [x] Every commit compiles
• [ ] Documentation checks
• [ ] Checkstyle
• [ ] Findbugs checks
• [ ] Build artifacts

In the 2.0.0 branch:

• [x] Every commit compiles
• [x] Documentation checks
• [x] Checkstyle
• [ ] Findbugs checks
• [x] Build artifacts

[Col-E]

https://github.com/Col-E/Recaf/blob/redesign/CONTRIBUTING.md#commit-messages - CI + versioning is now automated with commit messages thanks to @ViRb3 - #196

[Col-E]

I'm going to close this as its basically complete. Findbugs can be easily added later, but for now I believe checkstyle will suffice.