Improved log fetching strategy -- sort files by date and cut off batch by total size.
Change schedule to every 20 minutes and 2 MB per run.
Increase the life span of cached user names.
Add static import for avg.
Expand the UniqueCountDao.
Upgrade spring-data-redis.
Add latency metrics for global latency, search, descendants; add a count metric for file downloads.
Per code review, add pipelining. Fix a bug with the timestamp field in the results.
Add logger.
Merge pull request #36 from eric-wu/master

Improve log fetching strategy