Updates gems. Re-adds rubygems source.

Heroku fails to find updated gem versions when Gemfile source is left
out.

Signed-off-by: Aleksandrs Ļedovskis <aleksandrs@ledovskis.lv>
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Acked-by: Austin Seipp <aseipp@pobox.com>