Refactored ActorSupport to shutdown actor system after test.
Re-did ActorSupport again. Ended up making it a fixture, and globally locking on GatlingActorSystem - only way to deal with the it being a singleton
ActorSupport locks on itself, not GatlingActorSystem
Merge branch 'master' of https://github.com/excilys/gatling

Conflicts:
	gatling-core/src/test/scala/io/gatling/core/action/PaceSpec.scala
	gatling-core/src/test/scala/io/gatling/core/structure/ExecsSpec.scala
Merge pull request #1755 from jamespic/actor-support

Actor support