Gitlab Issues integration update

I finally updated the Gitlab Issues Integraiton. Sorry for such delay. Integration was working well, so this is just cosmetic update. The only problem was with tracker url. Previously gitlab accepted http://gitlab/ID/issues, while now you have to use namespace/project name http://gitlab/namespace/project/issues. I added field into configuration to use it. I also updated old dependency for gitlab gem. Unfortunately I couldnt pass bundle install on my mac, (issue with libv8), so someone pls finish Gemfile.lock. I tested it on my instance of errbit. Worked well for me.