modernized the build

* update SBT to a stable version (0.12.1)
* update pgp plugin accordingly
* drop support for Scala 2.9.0-1
* add support for Scala 2.10.0
* simplified the build file
whitespace
use the same .travis.yml in master as in scalaz-seven
Fixes #57: StreamT.isEmpty
update Scalacheck to 1.10.0
Scala 2.9.3-RC1
Use sbt-extras from travis and extend build matrix
Merge pull request #244 from gildegoma/use-travis-sbt-extras

Use sbt-extras directly from Travis CI default environment
Travis CI: Add OpenJDK 7 to build matrix
Merge pull request #246 from gildegoma/travisci-add-openjdk

Travis CI: Add OpenJDK 7 to build matrix
update SBT plugin
remove release notes from the repository, they're now in the wiki
build against 2.9.3 and 2.10.1, drop 2.9.1 support