Use https to clone Github3.py

Using the git protocol makes it hard to fetch the repo if internet
access is only possible via a proxy. An easy fix is using the https
protocol. That way the http_proxy vars on the host are automatically
obeyed and the clone via proxy works.

Change-Id: I18d75b5a16c809ac2d7834e91d32617017aea7f8

requirements.txt

@@ -2,7 +2,7 @@ pbr>=1.1.0
 
 # pull from master until https://github.com/sigmavirus24/github3.py/pull/671
 # is in a release
--e git://github.com/sigmavirus24/github3.py.git@develop#egg=Github3.py
+-e git+https://github.com/sigmavirus24/github3.py.git@develop#egg=Github3.py
 PyYAML>=3.1.0
 Paste
 WebOb>=1.2.3