Haproxystats

* Remove unnecessary server metrics
* Disable computation of stats across all backends

* Introduce queue-size for pull program
* Log exception when we fail to send data to graphite
* Avoid leaking FD when connection timeout
* Log when we close TCP connection to graphite
* Rewrite comment

* Set timeout on TCP socket for graphite handler

* Avoid a crash if incoming directory can't be removed
* Log version on startup

* Catch few more Connection exceptions on close
* Report wall clock time for pulling statistics
* Emit an error when we fail to remove temporary dir
* Add retry logic on connections to UNIX sockets
* Warn if tasks are canceled when reach pull-timeout
* More reasonable values for pull retry logic
* Update TODO
* Fix a regression introduced by b61ce6bcc
* Remove unused variable
* Remove unnecessary space
* Rename parameter signal to signalname
* Rearrange log messages when parsing sites stats
* Rearrange log messages when parsing daemon stats
* Error if Pandas data frame is empty
* Prevent passing empty data to Pandas
* Reorder log messages and change severities
* Warn if data directory doesn't have any files

* Catch socket.timeout
* Log filenames in debug mode