Fix instructions for bintray jcenter
Fix instructions for bintray jcenter

Using bintray jcenter over HTTP is now unsupported: https://jfrog.com/jcenter-http/

So the instructions for adding the lib for SBT did not work anymore.
This fixes it by using SBT's predefined resolver definition for JCenter Bintray, which uses HTTPS.
dehora/nakadi-java