race#show should include stats on registered teams & link to race/:race_id/registrations

[ometa]

When the stats for past races was removed from the rendering (in #87), the useful link to show the registered teams effectively disappeared. This makes it impossible for a refunder to access the teams to refund once the race has happened, since the formerly-displayed link is no longer visible.

The route they need still works, but it should be easy to find and use.

Tasks:

• Ensure this page (https://dogtag.chiditarod.org/races/5/) has a link to this page (https://dogtag.chiditarod.org/races/5/registrations)
• Ensure that the https://dogtag.chiditarod.org/races/5/ page displays # of teams fully registered, basic stats, etc.