More handlers and dedup code

[wshafer]

Added SamplingHandler
Added NullHandler
Added PsrHandler
Added TestHandler

Converted ClientTrait to ServiceTrait to cut down on
un-needed code duplication

[codecov-io]

Codecov Report

Merging #3 into master will increase coverage by 0.09%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master      #3      +/-   ##
===========================================
+ Coverage        99%   99.1%   +0.09%     
+ Complexity      271     265       -6     
===========================================
  Files            82      86       +4     
  Lines          1010    1002       -8     
===========================================
- Hits           1000     993       -7     
+ Misses           10       9       -1

Impacted Files	Coverage Δ	Complexity Δ
src/Service/AbstractServiceManager.php	100% <ø> (+2.38%)	16 <0> (ø)	⬇️
src/Handler/SwiftMessageTrait.php	100% <ø> (ø)	4 <0> (ø)	⬇️
src/Handler/RavenHandlerFactory.php	100% <100%> (ø)	1 <0> (-3)	⬇️
src/Handler/AmqpHandlerFactory.php	100% <100%> (ø)	1 <0> (-3)	⬇️
src/Handler/RedisHandlerFactory.php	100% <100%> (ø)	1 <0> (ø)	⬇️
src/Handler/NullHandlerFactory.php	100% <100%> (ø)	1 <1> (?)
src/Handler/ElasticSearchHandlerFactory.php	100% <100%> (ø)	1 <0> (ø)	⬇️
src/Handler/MongoDBHandlerFactory.php	100% <100%> (ø)	1 <0> (ø)	⬇️
src/Handler/HandlerMapper.php	100% <100%> (ø)	46 <0> (+4)	⬆️
src/Handler/GelfHandlerFactory.php	100% <100%> (ø)	1 <0> (-3)	⬇️
... and 13 more

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