fix vouch#368 build on FreeBSD and Linux

vouch#344 formatting, add README entry

fix vouch#361 with go modules, upgrade Docker to go 1.15

vouch#354 clarify audience (aud) check

* move claims.Sites into claims.Audience
* move check Site to check Audience
* general cleanup
* rename CreateUserTokenString to NewVPJWT

Merge branch 'feature/coveralls'

Merge branch 'pr/gsx95/350'

run `do.sh bug_report` in alpine docker container

vouch#341 adjust scopes_and_claims file name

vouch#297 create self signed certs

Merge branch 'pr/Husseinfo/307'