methods/el-get-github: change the default url type to https

All git repositories should be fetched over HTTPS by default, to allow
authenticated pushes to the user's own repositories.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Merge pull request #1064 from artagnon/master

methods/el-get-github: change the default url type to https