Add custom ssh port support and fix a small permission problem

First about `sudo chmod -R 750 /home/git/.gitolite/`. When I first install gitlab as the Guide. The check program always say `post-receive exists? ............NO`. And I found that User GitLab can not even see the post-receive file. So I add this option and then the problem is solved. I don't know if there is better choice to fix this. Maybe somebody else have a better idea?

Second I add the custom SSH port support. In many VPS systems, the SSH port is sometimes not 22. So I think this is very important. After create the config file, the git will work correctly.