Allow matching rules by scheme

The second commit of this pull request allows a new option to control the protocol that have to match the request. This allows us to make redirects of the same page from http to https, for example:

    r301 '/some-page', 'https://host.com/some-page', :scheme => 'http'

The first commit is only a cleanup of whitespaces, which I can discard if you want.

*UPDATE*: Also this fix: Gemfile.lock removed from gemspec.