fix populateCache flag not working
cosmetics
add CachingClusteredClient tests
add disable populate / use cache tests
Use druid implementation of HyperLogLog

remove dependency on clear spring analytics
Merge pull request #421 from metamx/use-druid-hyperloglog

Use druid implementation of HyperLogLog
Merge pull request #417 from metamx/fix-caching-bug

Fix caching bug and add CachingClusteredClient tests