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
skip doc generation
remove erroneous version from Heroku plugin
Merge pull request #43 from heroku/no-doc-gen

No doc gen
Merge remote-tracking branch 'upstream/master'
don't remove ivy cache (see if it speeds up build