Better object caching

[dlareau]

This is issue 1/3 spawned from the closing of #11.
The server right now does nothing except the default database query caching, which is becoming not enough.

The server should work alongside a caching framework such as memcached to store user sessions, commonly accessed objects (like the current hunt, team, and puzzle data), and other various things.

[dlareau]

Thought: Consider divorcing re-usable content from individual content on most pages. The overall pages would be cached and any individualism (previous answers, which puzzles are solved) would be loaded in a separate ajax request after the initial page loads.

[dlareau]

If this can work, consider also somehow doing this for the navbar, which is the only thing stopping most pages from being cached for logged in users.