Update git-client plugin version dependency to 1.6.1

Use latest released git client plugin so that test builds pass in
BuildHive and elsewhere.
Add jacoco coverage reporting
Merge pull request #190 from MarkEWaite/master-add-jacoco-coverage

Add jacoco coverage reporting and update surefire plugin version
Merge pull request #189 from MarkEWaite/master-update-git-client-version-1.6.1

Update git-client plugin version dependency to 1.6.1