Fix jsr305 build issue and add .gitignore

The jsr305 2.0.2 => 3.0.0 version upgrade was incomplete in commit 5e71dc2571a0a9d689d40e01c0f6cf095ca6d794

The .gitignore is of course useful for everyone submitting changes.

I signed and submitted a scanned copy of the Google CLA agreement just prior to creating this request. There are no issues associated with this PR but I will create them for more substantive changes in the future.