Update akka-docs/rst/general/actor-systems.rst
Update akka-docs/rst/general/actor-systems.rst

Replace "with respect fault-handling" with "with respect to fault-handling".
Merge pull request #1035 from derekmahar/patch-3

Update akka-docs/rst/general/actor-systems.rst
add debug helper for CallingThreadDispatcherModelSpec, see #2821

- the problem is that the user guardian gets blocked for more than 3
  seconds, and I have no clue who blocks it where
- therefore print all stack traces two seconds into the test if still
  not finished
 #2775 - Adding migration guide for waiting on promises
Unwatch watched actors on termination. Fixes: #2923

unwatchWatchedActors must stay in finishTerminate as an emergency stop might occur at handleInvokeFailure
added basic support for Epub generation
 #2782 - Removing ConcurrentIdentityHashMap and shake this all about
 isProxy is internally using a single, fat, synchronized – yes, astonishing to say the least, with this we lower the pressure on that lock.
Merge pull request #1041 from RickLatrine/wip-2923-terminated-cascade-ricklatrine

Prevents Terminated message cascade, see #2923
Merge pull request #1046 from tlockney/feature/epub-support

added basic support for Epub generation
Merge pull request #1048 from akka/wip-2782-removing-CIHM-√

 #2782 - Removing ConcurrentIdentityHashMap and shake this all about
Merge pull request #1049 from akka/wip-lower-pressure-on-lock-√

 isProxy is internally using a single, fat, synchronized – yes, astonish...
LightArrayRevolverScheduler, see #2904

- based on a wheel (AtomicReferenceArray) from which atomic
  single-linked lists dangle
- no locks
- deterministic tests due to overridable time source
- also bring docs up to date
Merge pull request #1027 from akka/wip-2904-timer-∂π

first cut of new AkkaTimer, see #2904
Java 6 again; plus forgot one copyright header
disable EPUB build until sbt-site is fixed, see #2938
relax too tight timing in FSMTransitionSpec