fix pre-version enforcement
Merge pull request #40 from julienledem/fix_preversion_enforcement

fix pre-version enforcement
[maven-release-plugin] prepare release 0.9.27
[maven-release-plugin] prepare for next development iteration
Fix #41: abstract could become concrete.
Merge pull request #42 from mschonaker/master

Fix #41: abstract could become concrete.
[maven-release-plugin] prepare release 0.9.28
[maven-release-plugin] prepare for next development iteration
[maven-release-plugin] prepare release 0.9.29
[maven-release-plugin] prepare for next development iteration
Update README.md