Better handling of API redirects

[smith]

We currently skip canonical redirection in Nginx if the user agent is "Faraday" (usually from Berkshelf) or "Ruby" (usually from Knife.)

This is a bit fragile and one of these solutions might work better:

• Don't do any redirection on the /api/* endpoints
• Don't attempt redirects for requests that are not HEAD or GET (because they shouldn't be followed anyway according to RFC 2616.)