update to latest version of Typesafe CONTRIBUTING rules
Merge pull request #1803 from akka/wip-CONTRIBUTING-∂π

update to latest version of Typesafe CONTRIBUTING rules
!per #3681 Performance and consistency improvements

- batch-write of persistent messages (user API)
- batch-write of events (in EventsourcedProcessor)
- command processing in EventsourcedProcessor by unstashing messages one-by-one from the internal stash
   * fixes performance issues that come up with unstashAll
- commands are not looped through journal actor but processed directly
- initial performance tests
  * command sourcing
  * event sourcing
  * event sourcing with user stash operations
- suppress stack traces in tests
Merge pull request #1808 from krasserm/wip-3681-performance-improvements-krasserm

!per #3681 Performance and consistency improvements
=doc Update Sphinx installation instructions
=doc,osg Effort to get OSGi integration tests running again

* Update protobuf dependency so mvn clean install runs again
* Bump OSGi version range in AkkaBuild to include current 2.3 for generated manifests
* Update path in dev documentation to correct TexBasic folder
Merge pull request #1817 from sandermak/osgi-sample-improvements

=doc,osg Effort to get OSGi integration tests running again
Merge pull request #1816 from akka/wip-sphinx-patriknw

=doc Update Sphinx installation instructions
=pro #3448 Upgrade to sbt 0.13.0
=all #3448 Newer Scalariform running on more files
Merge pull request #1791 from akka/wip-3448-update-to-sbt-0.13-ban

=pro #3448 Upgrade to sbt 0.13.0
=act #3601 Harden test for log dead letters
=act,rem #3073 Make ActorSelection faster
Merge pull request #1813 from akka/wip-3073-faster-actorselection-patriknw

=act,rem #3073 Make ActorSelection faster
Merge pull request #1820 from akka/wip-3601-ActorSystemSpec-patriknw

=act #3601 Harden test for log dead letters