Update documentation/manual/scalaGuide/main/akka/ScalaAkka.md

Akka now uses Duration from Scala core.
Merge pull request #702 from ndeverge/patch-3

Update documentation/manual/scalaGuide/main/akka/ScalaAkka.md
Added new documentation for play 2 http api
Documentation for new http api
Update documentation/manual/Highlights.md
merged from dev/master