Use GitHub-style hypermedia URLs

I like their *_url approach as opposed to the more verbose "links"=>[{"rel"=>"self", "href"=>url}]

When querying a specific location, the response now also includes an array containing the URLs of other locations that belong to the same organization as the location currently being viewed.
Add hypermedia links to API root
Add org URL to organization key in search response
Add rate_limit endpoint
Prevent home page access from bombing when Accept Header is passed
Throttle requests with & w/o api token separately
Update root hypermedia links
Don't hardcode URLs
Fix link header pagination info

I was slicing everything from the request params except for page, which means that search parameters were getting stripped off. Now I'm only slicing the extra stuff that Grape adds.
Fix link header bug for empty results collection

When there are no results, current_page = 1, but total_pages = 0.  The Tire gem overrides Kaminari's last_page? method which checks if current_page >= total_pages, but tire defines last_page? as current_page == total_pages, which is semantically correct, but breaks our code.

Kaminari also provides an out_of_range? method to check if current_page > total_pages. However, Tire uses out_of_bounds? and didn't alias out_of_range?, so I submitted a pull request. Until he merges the fix, I will be using my fork of tire.

The alias is important because our app depends on 2 different pagination methods. Non-search queries (such as /api/locations) are paginated by Kaminari, but search results are paginated by Tire. Aliasing saves us from cluttering our code with multiple conditional statements.