Update versions of used libraries/plugins#68

Merged

zmeda merged 2 commits intoscala-jsonapi:masterfrom

jmhofer:issue/67

Aug 5, 2016

Commits on Aug 5, 2016

Update sbt, scoverage, coveralls, circe, akka, scalatest versions to the respective latest ones.
jmhofer
committed
Add `coverageReport` target to the Travis `after_success` step as described in the docs to coveralls.
jmhofer
committed