v1.3.0

• Now fullname() uses the FULLNAME environment variable, if set.

• Now email_address() uses the EMAIL environment variable, if set.

v1.2.0

• gh_username() caches the result, separately for each email address.

• gh_username() uses the GITHUB_USERNAME environment variable, if it
  it is set (#6, @maelle)

• On Windows, gh_fullname() and gh_email_address() try finding the
  global git configuration in Sys.getenv("USERPROFILE") if it is not
  found in Sys.getenv("HOME") (#7, @maelle)

• gh_username() also tries the GITHUB_PAT environment variable
  to find a GitHub token, after GITHUB_TOKEN (#9, @maelle)