- update to play 2.3 version

Update plugin and sample code to play 2.3.
- use URLConnection instead of WS to get ride of implicit Application

Could not use WS in the enabled method call that cause a infinite loop
because the WSPlugin needs Application instance that has all plugins
loaded so it try to load the IronCachePlugin again and that this
cycle goes on the IronCachePlugin loads the WSPLugin, ...
- set typesafe resolver

To use the IronCachePlugin as git dependency it was needed
to add the TypeSafe release repo to the resolvers in the Build.scala
otherwise the play cache could not be found.
- added TODO use WS during plugin enabled method

WS could not be used with provided Plugin application in the enabled
method that casue a infinite loop because enabled method is infinite called
from WSPlugin initialisation.