Refactoring: add a RawCache trait (a facade for Shade's Memcached trait)
Refactoring: rename some traits and classes, fix some comments

* CacheClient -> CacheOps
* CacheAccessor -> Cache
* NoCache* -> DummyCache*
More refactoring: rename package, move some traits

* cache.client -> cache.memcached
* Move all non-Memcached-specific stuff to parent cache package
* move tests to correct packages
Merge pull request #28 from m3dev/feature/cache-refactoring

Great work :+1+ caching definitely needed some loving.