Update AHC 1.9.3
Fix build
Remove dead code
missing empty line
Migrate code examples to Scala classes, close #2432
Merge pull request #2443 from gatling/docs-includecode-migration

Doc: Migrate code examples to Scala classes
Retry connections to Graphite if it failed, close #2440
Introduce a SupervisorStrategy to limit conn. retries to Graphite
Rename Sse.get into Sse.open
Upgrade Mockito 1.10.6
Upgrade SLF4J 1.7.8
Upgrade scala-parser-combinators 1.0.3
Upgrade H2 1.4.183
Upgrade scopt 3.3.0
Fix SSE checks
Doc: Add 3rd and 4th percentile doc in Cheat Sheet
Document sse.cancel
minor clean up
Fix anchors
Doc: Move Assertions above HTTP in Cheat Sheet