Prepare for releasing v0.12.0

updated changelog

[maven-release-plugin] copy for tag 0.10.0

removed Java 1.6 from .travis.yml

Set version to 0.8.1

v0.8.0

Bumped verstion to 0.7.0

Release v0.6.0 on 2013-10-15

[maven-release-plugin] copy for tag 0.5.1

v0.5 tag from trunk r173.