Fix the repo regex to handle + in URLs.
Fix the repo regex to handle + in URLs.

The documentation said that you could do git+https:// or git+ssh:// but
that was not, in fact, true.

terryjbates/cookiecutter,audreyr/cookiecutter,willingc/cookiecutter,luzfcb/cookiecutter,Springerle/cookiecutter,willingc/cookiecutter,dajose/cookiecutter,luzfcb/cookiecutter,hackebrot/cookiecutter,terryjbates/cookiecutter,stevepiercy/cookiecutter,stevepiercy/cookiecutter,hackebrot/cookiecutter,pjbull/cookiecutter,michaeljoseph/cookiecutter,audreyr/cookiecutter,pjbull/cookiecutter,Springerle/cookiecutter,dajose/cookiecutter,michaeljoseph/cookiecutter