Add date to release notes and note on dropping python 2 support.

Update verison to 3.6.rc1.

v3.5 Final

First release candidate for version 3.5

REL tag version 3.4.1

REL tag version 3.4rc2

REL tag version 3.4rc1

REL tag version 3.3

REL tag version 3.3rc2

REL tag version 3.3.rc1