Extend git-plugin with --match Option

Hi konrad,
it's me once again ;)
I extended the describe-option of the git-commit-id-plugin with the match-Option (@see: https://github.com/ktoso/maven-git-commit-id-plugin/issues/97).

Any suggestions for improvements are welcome.

BTW: I updated the README a bit...change it if you don't like the description ;)