Pghero

- Added invalid indexes
- Fixed RDS stats for aws-sdk 2

- Added `tables` option to `create_user` method
- Added ability to sort query stats by average_time and calls
- Only show unused indexes with no index scans in UI

- Added historical query stats

- Fixed connection bad errors
- Restore previous connection properly for nested with blocks
- Added analyze button to explain page
- Added explain button to live queries page

- More platforms!
- Support for multiple databases!
- Added `replica?` method
- Added `replication_lag` method
- Added `ssl_used?` method
- Added `kill_long_running_queries` method
- Added env vars for settings

- Added connections page
- Added message for insufficient privilege
- Added `ip` to `connection_sources`