Use Garner::Strategies::Context::Key::Base strategy

This is just a minor issue to capitalize on inheritance.
Merge pull request #64 from potomak/capitalize-on-inheritance

Use Garner::Strategies::Context::Key::Base strategy
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.
Merge pull request #73 from dblock/fix-72

Fix: ActiveRecord 4 cache_key is now in :nsec format.
Removed Jeweler.
Merge pull request #74 from dblock/gemspec

Removed Jeweler.
Added Rubocop, Ruby-style linter.
Merge pull request #76 from dblock/rubocop

Added Rubocop, Ruby-style linter.
Run tests on JRuby.
Fixed RSpec deprecation warnings.
Merge pull request #77 from dblock/jruby-fix

Run tests on JRuby.
Added CONTRIBUTING.md, please contribute and we love you.
Preparing for release, 0.5.0.
Preparing for next development iteration, 0.5.1.
Corrected reference to the current stable Garner release in README.
Fix typo on Garner mongoid_identity_fields configuration
Merge pull request #79 from praditus/master

Fix typo on Garner mongoid_identity_fields configuration