missing subcommands for hotfix

[gucki]

git-flow-completion misses some subcommands for hotfix:

git flow hotfix 
-> finish   help     list     start    

git flow hotfix help 
usage: git flow hotfix [list] [-v]
   git flow hotfix start [-F] <version> [<base>]
   git flow hotfix finish [-Fsumpk] <version>
   git flow hotfix publish <version>
   git flow hotfix track <version>

[gucki]

Pull request is here now: #22