Bump to sbt 0.13.17-RC1 for Java 9 support.
Bump to sbt 0.13.17-RC1 for Java 9 support.

We'll want to get going on Scala 2.12 and sbt 1.0 soon, but for now let's keep
our eye on the 1.1.0 release ball.

hacklanta/lift-formality