The `# -*- coding: utf-8 -*-` headers were useful for Python 2, and
aren't needed for Python 3 where UTF-8 is the default.
yamllint support of Python 2 was dropped in early 2021, see commit
a3fc64d "End support for Python 2".
Let's drop these headers.
There is a backwards-incompatible change in PyYAML that induces a crash
if `check_token()` is not called before `peek_token()`. See commit
a02d17a in PyYAML or https://github.com/yaml/pyyaml/pull/150.
Closes#105.
Instead of iterating over lines and tokens (and find comments between
tokens in the comment rules), add a new `Comment` type and set rules
with `type = 'comment'`.
