A simple caching output controller for Savant

Savant output can be cached for faster rendering. PEAR2_Templates_Savant_Turbo allows rendered content to be cached, and reused for subsequent requests. For basic use, instead of creating a new PEAR2TemplatesSavantMain object, create a PEAR2TemplatesSavantTurbo object. In models you'd like to have cached, implement the CacheableInterface.