allow sbt 0.12.0 to be a supported version
fail fast on curl downloads
add opt/sbt-0.12.0.boot.properties
fail fast on sbt download
replace sed piping on downloads with useful error
change error message when sbt version is in prelim check range but not actually having a prop file to declare unsupported
change version numbers in tests for future compatibility
Merge pull request #23 from heroku/sbt-0.12.0

SBT 0.12.0 Support
Reviewed by @naamannewbold
remove download of heroku-plugins-0.11.3.sbt config
Merge pull request #24 from heroku/dedupe-heroku-sbt-typesafe

remove download of heroku-plugins-0.11.3.sbt config
first attempt at multi-jdk support
remove unneeded stuff and auto-set PATH to include jdk
Use assertCapturedEquals for release_test.sh
Merge pull request #25 from jamesward/multi-jdk

Multi JDK
fix release_test to look for .jdk/bin: in path
Add sbt.boot.properties to git repo and source locally instead of from s3
copy heroku sbt plugin directly from opt dir instead of downloading
remove unused sbt-0.11.0
add sbt-0.12.1.boot.properties
Overlay JDK