ignore Gemfile.local
Load Gemfile.local if exists
formatting
use source argument if set
(maint) fix gemfile for win
(maint) formatting
Adding specs for source parameter

This adds a few specs to make sure that source defaults to nil
which uses whatever chocolatey uses by default. This checks that
it will accept local paths and http locations. It also ensures that
when specified, it is used with install and update.