Add Cache tests
Add Cache tests

Just testing memcache for now.

SEL-Columbia/TileStache,mojodna/TileStache,Billups/TileStache,Kosta-Github/TileStache,TileStache/TileStache,mojodna/TileStache,moskvax/TileStache,moskvax/TileStache,mapzen/TileStache,Billups/TileStache,Kosta-Github/TileStache,Billups/TileStache,jbants/TileStache,jbants/TileStache,Kosta-Github/TileStache,mapzen/TileStache,TileStache/TileStache,Blechhirn/TileStache,Blechhirn/TileStache,MetGIS/TileStache,SEL-Columbia/TileStache,mapzen/TileStache,MetGIS/TileStache,Blechhirn/TileStache,MetGIS/TileStache,jbants/TileStache,moskvax/TileStache,SEL-Columbia/TileStache,TileStache/TileStache