MOAR PERF!!

Found daybreak, an EXTREMELY fast in-memory cache backed by a file.

Also found that creating new caches all the time really hurts perf.

Lastly, the overhead of creating a new thread in Ruby (or at least with
Parallel) is more expensive than running through everything in one
thread.
Minor changes in the daybreak cache

* Fixed docs
* No longer loading on each read
* flushing after each write