add sbt-0.12.3 support
Merge pull request #40 from xuwei-k/sbt0.12.3

add sbt-0.12.3 support
Always vendor JDK
Merge pull request #41 from heroku/vendorjdk

Always vendor JDK
Skip logging
Merge branch 'master' of https://github.com/heroku/heroku-buildpack-scala into mongo-2.3