Added twig filter to edit the source url

Added a twig filter to turn urls like `git@bitbucket.org:Comapny/repo.git` into `http://bitbucket.org/Comapny/repo.git`

Without this fix, the link to any release would be `http://satis-domain.com/git@bitbucket.org:Comapny/repo.git`. 
Hmm in my installation the release links are pointing to the dist packages on the satis server, not to the source repos.