Add support for Kotlin

[nedtwigg]

With Kotlin build scripts coming, it would be great for Spotless to add support for kotlin. shyiko/ktlint seems to be the main entry in this space.

Added a first cut in feature/kotlin, but it's pretty difficult to integrate via reflection at the moment because some of the args are hard to instantiate (code). Should be easy to fix with a small change on the library side, I'll contact the author there.

[nedtwigg]

Initial support for ktlint is now available in 3.1.0-SNAPSHOT.

[nedtwigg]

Tested on some random projects, but wildcard imports seem to be a common pattern, which ktlint doesn't allow. Gonna see if there's an easy way to ignore this particular rule.

pinterest/ktlint#21

[nedtwigg]

Released in 3.1.0.