Leverage CAS
Bump to released memcached_store gem
Don't pretend we'll support jruby soon
Replace .to_h for pre-2.1 rubby
Spy needs after_teardown in minitest

tenderlove introduced after_teardown in minitest 2.11.0. Rubby 1.9.3
ships with an earlier release.
Add deleted-fetch bm and tests for fetch conflict
Add conflict benchmarks
Split responsibilities of MemoizedCacheProxy

MemoizedCacheProxy should only be responsible for memoizing. Cache
fetching responsibility is moved to a new CacheFetcher class.
Address review comments, bump serialized version
Bump to released memcached_store gem
Merge pull request #154 from Shopify/cas2

Leverage CAS