Release 1.3.1

See the 1.3.1 milestone for the full list of related tickets and PRs.

Enhancements

1. Bump Paradox to version 0.3.0 and support the Paradox site plugin for sbt 1.0. #111 by @jonas

Fixes

1. Enable sbt-ghpages integration test for sbt 1.0. #110 by @xuwei-k