Add git-buildpackage to extras packages needed for a builder

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Add parsing debian changelog package
Update packages_extra_spec.rb with new packages

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #19 from MosesMendoza/add_git_buildpackage

Add git-buildpackage to extras packages needed for a builder