Complete code coverage for capakey gateway caching.
Don't pickle the gateway.

Not a good idea to add the gateway itself to the cache. When using eg.
the dogpile dbm backend, the result returned from the creator gets
pickled. Fails horribly when the gateway is in there.
Fixed an error in capakey parsing regex.
Added example scripts for capakey gateway.

With and without caching.
Ignore dogpile caching dir.
Add some docs about caching.