Merge pull request #29 from ScotterC/association_cache

breaking up association cache methods
Merge pull request #30 from ScotterC/belongs-polymorphic-nil

Polymorphics don't necessarily have a type set.
Merge pull request #31 from ScotterC/return-nil-for-one-to-one

Return nil for one to one
Memoizing method and association cache methods.
Handling bangs and queries
Merge pull request #34 from ScotterC/memoization

Memoizing method and association cache methods.
Add class method marshalling specs
Merge branch 'master' of github.com:flyerhzm/simple_cacheable into marshalling-tests
Merge pull request #35 from pathouse/marshalling-tests

Marshalling tests
Encode and decode models for cache read/write
misspellings, nil value check on read, missing parens
Spelling error, ActiveRecord::Assocation... to_a
Singleton fetch, spec fixes, model_fetch_spec
Address Comments

Main method names changed to fetch and fetch_associated. Accept blocks.
Only write if read from cache is nil.
Single fetch method
Spec fixes
single fetch method
fix typo
Address comments
Instance cache key class method, coder lambdas delegate to method