Fix some TODO in build settings

 - Remove ls-sbt (https://github.com/scalatra/scalatra/pull/423 )
 - Note about scalaz-7.0.x compatibility (https://github.com/scalatra/scalatra/pull/425)
 - Back to Scala 2.11.2 for now
Merge pull request #426 from seratch/feature/fix-build-settings

Fix some TODO in build settings