Merge pull request #5 from ktf/allow-scramless-checkout

Allow git-cms-addpkg to work also outside a release area.
Merge pull request #6 from ktf/branch-workflow

Branch workflow
Use official-cmssw in place of cms-official.
Use SSH URL, not HTTPS, since on slc5 there is no way to use the credential
helper.
Misc cleanups:

- Add --https option to use HTTPS access method rather than default ssh one.
- -q is now really quiet.