Fully working implementation

I went through what had been started and finished the plugin. It implements all of the functions Core specifies and by extension, their methods in `WP_Object_Cache`.

I also added support for the [Redis PECL module](http://pecl.php.net/package/redis) and better error handling for failed Redis connections.

I've been using it on my personal site ([ethitter.com](https://ethitter.com/)) for a few days without issue. It could surely use further review before widespread use, but we're close to something worth releasing!