Prepare to release 0.22

Migrate to com.google.truth groupId

Add a relocation pom.

Bump version for 0.20 Release:

  * Bugfix to named() to support primitive array subjects properly.
  * Bugfix to float-comparing subjects where they handled float equality inappropriately.

Bump version to 0.19

Prepare to release 0.18

Bump version for release.

Update version for release 0.16

Bump version to 0.15 in preparation for release.

Bump poms and readme to reflect release 0.13