remove unused variable
extract function github_get_conn, supply (currently failing) tests
don't throw error when installing a pull request from GitHub using the format user/repo#pull
don't pass repo.zip as download name, adds confusion with the new repo syntax
install_github stores effective parameters (as found when parsing repo argument) in DESCRIPTION
Merge pull request #390 from krlmlr/388-install-gh-pull

don't throw error when installing a pull request from GitHub using the format user/repo#pull