update tests to 0.8.2-SNAPSHOT
upgrade current compatible version to 0.13.2
build 0.13 version against 0.13.2, fixes #28 (for whatever reason)
don't use minor sbt version number if it wasn't supplied, fixes #29
add notes for 0.8.2
Merge branch 'master' of github.com:jrudolph/sbt-cross-building

Conflicts:
	src/main/scala/sbt/CrossBuilding.scala