Merge upstream

* master: (21 commits)
  Update README.md
  Unconditionally add forward slash in OCSP GET requests (square#282)
  Use Go generate instead of a makefile (square#279)
  Bump github.com/stretchr/testify from 1.7.5 to 1.8.0
  Add support for printing SCTs (square#277)
  Update Go version to 1.18 (square#276)
  Update to 1.16 (square#275)
  Fix OCSP checking (square#274)
  Bump github.com/stretchr/testify from 1.7.2 to 1.7.5
  Update go command to install certigo (square#270)
  Bump github.com/stretchr/testify from 1.7.1 to 1.7.2
  Upgrade yaml.v3 version (square#266)
  Allow any ciphersuite in TestConnect (square#268)
  Fix TestConnect on macOS (square#265)
  Bump github.com/stretchr/testify from 1.7.0 to 1.7.1 (square#262)
  Bump version string to 1.15.1 (square#263)
  Remove use of the format list in the connect command (square#260)
  Add --leaf flag to view the first cert only, including for json and pem
  Set certs explicitly (square#259)
  Upgrade /x/crypto dependency (square#257)
  ...