cross-compile for scala 2.11/2.10
use spray repo while spray-json 1.2.6 propagates
scala-2.10 compatible reflection code

It generates warnings, but it works in both versions. We'll have to extract this specific piece of code and use per-scala-version folders (src/main/scala_2.10, src/main/scala_2.11) to overcome otherwise.
Merge pull request #73 from SpinGo/master

scala 2.10/2.11 cross building against slick 2.1.0-M2