Implement Caching

[funnylookinhat]

BeansBooks works with and returns a large volume of extremely verbose objects - some of these will be worth caching even after making improvements to the search results as referenced in Issue #31 . We need to evaluate implementing a standard caching interface ( Kohana::Cache is the obvious choice ) and establish a basis for what objects should be cached, when they should be cached, and for how long along with a valid procedure for updating cached objects.

Wrapped up in this discussion is the determination as to whether it is good practice for BeansBooks to depend upon Kohana modules. Technically speaking, the design pattern used for BeansBooks backend code should have no dependencies outside of the classes/ folder wherein it resides. To change this would be a significant undertaking and only worth pursuing if it significantly improved the long-term outlook for the code-base while also maintaining feature-parity.