Refactored Cache::Helpers and added documentation.
Refactored Cache::Helpers and added documentation.

* Removed un-needed dependencies
* Added extensive documentation.
* Refactored #cache_fragment() method.
* Deprecated the #cache() method.
* Refactored #cache_expire() method.
* Updated parts of the code to Sinatra 1.0a support.
* Refactored private methods.
* Cleaned up the default configuration settings.
* Added support for Sinatra::Settings (if available)

kematzy/sinatra-cache,arturo-c/sinatra-cache