Checks whether to add Echo shim or not based on Echo supported version o...

...f Akka and Play.

Checks the supported version based on hard coded values in the Dependencies.scala file. Not the most elegant solution but it gets the job done. In order for an Echo shim to be added it needs to fulfil all of the following criteria:

* If Akka present the version <= supported version (sbt 0.12 = Akka 2.2.1 and sbt 0.13 = Akka 2.2.1)
* If Play present version <= supported version (sbt 0.12 = Play 2.1.4 and sbt 0.13 = Play 2.2.0)
* Has Echo enabled