Added cleanup of cache after test
Chaning the CacheItemModel to use defined types instead of objects
Adding test to CacheShould
Possible optimization of cache tab
Changed CacheItemModel properties to nullable.
Corresponding change in Cache.cs

Minor tidy up

Added a ReturnData test to CacheShould

Moving assignment of two values outside a loop.
Expanding try/catch.
Merge branch 'cacheTab' of https://github.com/bryanjhogan/Glimpse into cacheTab

Conflicts:
	source/Glimpse.AspNet/Tab/Cache.cs