Feature/add gomemcache

Add optional golang based gomemcache library. 
This library does not require libmemcached, and provides it's own pooling, but does not offer the level of control that gomc does. This library has NOT yet been fully load tested.

@bbangert || @kitcambridge r?
Style is to have the err check afterward handle the case where its an error that should be acted on. I'll admit this err condition confuses me somewhat, if there's no err, return nil, that part makes sense. Or if it's any error at all, as long as its not a ErrCacheMiss, its still ok?