Refactored GelfSenderFactory for use of common GelfSender implementation
outside the core project (including tests)

Refactored/Fixed GelfREDISSender for use in multihreaded environment
Removed unused method
Added possibility to configure connection-string without port (and take
port from configuration)
Fixed bug on jedis pool caching
Merge pull request #17 from Batigoal/master

Redis bugfix and GelfSender flexibility