Add Scala linter to CI

[bzz]

TODO:

• add/document sbt task with linter and code style
• integrate linter in CI

As well noted in #48 (review)

I would be nice if all of us use the same configuration for code style.

[carlosms]

It looks like we already have sbt scalastyle in place. As can be seen in travis.yml, and travis logs.

I'll wait for you to close the issue, just in case I misunderstood it and there's something else missing.

[smacker]

Is it possible to catch such things:

• https://github.com/src-d/gemini/pull/48/files#diff-7d8cae56157bb5c2c2053b9797014e8f
• https://github.com/src-d/gemini/pull/48/files#diff-768357618a8db6a4da444273c800e8d9
• https://github.com/src-d/gemini/pull/48/files#diff-747eed6d907b7380e439aec919e624c6R169

by linter/codestyle?

[bzz]

Those are basically default InteliJ scala styles. 👍 for importing them to our scalastyle profile, so CI could verify.

@carlosms please feel free to update pr description with your finds/changes in scope.

[bzz]

Addressed by #86 now