SSH URL Update

Hi guys.
- Small tweak to allow SSH URLS to be added.
- Accepts GH and non GH SSH URLS
- Conforms with Sismo's formatting for @branch

IE:
$projects[] = new Sismo\GithubProject('Project Dev Branch', 'git@github.com:people/project.git@dev', $notifier);
or just as happily
$projects[] = new Sismo\GithubProject('Project Dev Branch', 'user@othersite.com:people/project.git', $notifier);

First PR, please be gentle.