Updating CHANGELOG for 0.20.0 release.
Updating CHANGELOG for 0.20.0 release.

rdelval/aurora,thinker0/aurora,thinker0/aurora,rdelval/aurora,apache/aurora,thinker0/aurora,medallia/aurora,medallia/aurora,thinker0/aurora,rdelval/aurora,apache/aurora,medallia/aurora,medallia/aurora,thinker0/aurora,apache/aurora,medallia/aurora,apache/aurora,medallia/aurora,apache/aurora,apache/aurora,rdelval/aurora,thinker0/aurora,rdelval/aurora,rdelval/aurora