Add Python 3.9 to the list of supported Python vesions.

Update version to 3.9.0

Update github issue template.

add pom.xml to manifest for sdist

Update pom.xml for final 3.8.0 release.

Fix rare bug in threading test.

Switch travis from oracle 7 jdk to openjdk 7 for migration to trusty.

increment version to 3.6.4

increment version to 3.6.3

update tests to use changed API