update README.md

fix DSL importing
Merge pull request #58 from antonmoiseev/patch-1

update README.md
Use the latest Spray nightly build
* bumps Akka to 2.2.0 final
* Spray 1.2-M8 has a memory link when used with Akka's SLF4J logging adapter
Setting version to 0.23.0
README.md updated to 0.23.0
Setting version to 0.24.0-SNAPSHOT
fixing AsyncResponseHandlerDSLSpecs
Merge branch 'master' into futures