Modern full text search

Hi there,

I think that if USV wants a modern HackerNews-like link sharing community, it deserves a modern search experience too :)

You'll find attached my 2 cents about plugging Algolia's Search API (http://www.algolia.com) in USV.com; it provides:
 - highlighting
 - instant-search
 - typo-tolerance
 - and custom ranking

Pagination and faceting haven't been plugged yet.

As you can see, I've added 4 setting keys that must be configured with your Algolia credentials (private mail with your login/passwd coming).

To initially export your MongoDB collection and import it in Algolia, you can use [this tool](https://github.com/algolia/algoliasearch-client-cmd/blob/master/mongodb/crawler). I used it on my local instance and it works well, please let me know if you have any issue with it: the code has been written recently.

I tried to follow your coding style guidelines and keep it working without Algolia.

Hope you'll like it!