Merge pull request #41 from ehmatthes/implement_caching

Implement caching
Merge pull request #42 from ehmatthes/implement_caching

All urls that should invalidate index cache are addressed.
Merge pull request #43 from ehmatthes/implement_caching

Implement caching
Merge pull request #44 from ehmatthes/implement_caching

Added first test, a test of invalidating the index cache.
Merge pull request #45 from ehmatthes/implement_caching

Implement caching
Fixed bug on invalidating discuss/id caches for double-digit id's.