Fixes #9, Fixes #7, Fixes #6, Fixes #4

Fixes #9 - Do not always push rendered html to case, push context if template is specified in decorator. 
Fixes #7 - Use smart_str on rendered html before pushing to cache. 
Fixes #6 - Add get_cache function that looks for viewlet backend before fallbacking on default. 
Fixes #4 - If no timeout is set on decorator use timeout to 2591999