Release gtfsio v1.0.0

[dhersz]

Prepare for release:

• [x] Check current CRAN check results
• [x] Polish NEWS
• [x] Draft new Zenodo version
• [x] Edit citation file
• [x] Update README
• [x] urlchecker::url_check() (will return that DOI links are not found, justify that on cran comments)
• [x] devtools::check(remote = TRUE, manual = TRUE)
• [x] devtools::check_win_oldrelease()
• [x] devtools::check_win_release()
• [x] devtools::check_win_devel()
• [x] rhub::check_for_cran(show_status = FALSE)
• [x] rhub::check_on_solaris(show_status = FALSE)
• [x] Clean up old revdep/ dir, build tar ball and move it to revdep/
• [x] result <- tools::check_packages_in_dir("revdep", check_args = "--as-cran", reverse = list())
• [x] Update cran-comments.md

Submit to CRAN:

• [x] Bump major version
• [x] Commit changes "v1.0.0 release"
• [x] devtools::submit_cran()
• [x] Approve email

Wait for CRAN...

• [x] Accepted
• [x] Submit tarball to Zenodo and review publication date
• [x] Create git tag and github release
• [ ] Tweet about it?