Fix gem dependencies
Add whiny_nils configuration variable to control behavior on nil bindings

* `Garner.config.whiny_nils?` also works
* New exception introduced: `Garner::Cache::NilBinding`
Merge pull request #70 from fancyremarker/whiny-nils

Add whiny_nils configuration variable to control behavior on nil bindings
Fix: ActiveRecord 4 cache_key is now in :nsec format.