Improved search for GIT_DIR (again)

Closes #21
Do not reset RevWalk instance in JGitRepository#getRevWalk()
Merge branch 'master' of github.com:koraktor/mavanagaiata

Conflicts:
	src/main/java/com/github/koraktor/mavanagaiata/mojo/AbstractGitMojo.java
small changes to accommodate internal API changes. Turn version back to non-snapshot