Merge pull request #6 from jordansjones/master

Remove unneeded assembly references.
Removing IRemovalListener since. Not necessary since ICache has an IObservable withthe events.
Add IStatsCounter interface.
Documentation for IStatsCounter
SimpleStatsCounter.
Fix typos. Apparently Jordan can't spell. :P
Abstract LoadingCache.
LoadingCache docs.
Forgot to commit a csproj change.