Allow ansible-galaxy to install roles from URLs

ansible-galaxy can now refer to SCM URLs (git and hg at this point)
for role names
Dependencies need to use the full SCM URLs too.
Otherwise all seems to work well

Test rolesfile
```
http://bitbucket.org/willthames/git-ansible-galaxy,v1.1
https://bitbucket.org/willthames/hg-ansible-galaxy
```
(works with ssh too)