Gravatar host is displayed CGI-escaped when not customized

Introduced by 0f785bbc

When no host value is set for Gravatar in gitlab.yml, it gets a default value in 1_settings.rb:

Settings.gravatar['plain_url']  ||= 'http://www.gravatar.com/avatar/%{hash}?s=%{size}&d=identicon'
Settings.gravatar['host']         = Settings.get_host_without_www(Settings.gravatar['plain_url'])

Where get_host_without_www does this:

    def get_host_without_www(url)
      url = CGI.escape(url)
      uri = URI.parse(url)
      uri = URI.parse("http://#{url}") if uri.scheme.nil?
      host = uri.host.downcase
      host.start_with?('www.') ? host[4..-1] : host
    end

Note the CGI.escape so that URI.parse doesn't fail due to the interpolation happening in the querystring. Unfortunately this makes uri.host return the full, escaped String rather than the www.gravatar.com we actually want. As a result, when you edit your profile, you see this monstrosity:

cc @stanhu @bbodenmiller