Fsfe-reuse

Fixed

- Any files with the suffix `.spdx` are no longer considered licenses.

Fixed

- The documentation now builds under Python 3.7.

Fixed

- When using reuse from a child directory using pygit2, correctly find
the root.

Changed

- The output of `reuse compile` is now deterministic. The files,
copyright lines and SPDX expressions are sorted alphabetically.

Fixed

- When a GPL license could not be found, the correct `-only` or
`-or-later` extension is now used in the warning message, rather
than a bare `GPL-3.0`.
- If you have a license listed as
`SPDX-Valid-License: GPL-3.0-or-later`, this now correctly matches
corresponding SPDX identifiers. Still it is recommended to use
`SPDX-Valid-License: GPL-3.0` instead.

Added

- Internationalisation support added. Initial support for:
- English.
- Dutch.
- Esperanto.
- Spanish.

Fixed

- The license list of SPDX 3.0 has deprecated `GPL-3.0` and `GPL-3.0+`
et al in favour of `GPL-3.0-only` and `GPL-3.0-or-later`. The
program has been amended to accommodate sufficiently for those
licenses.

Changed

- `Project.reuse_info_of` now extracts, combines and returns
information both from the file itself and from debian/copyright.
- `ReuseInfo` now holds sets instead of lists.
- As a result of this, `ReuseInfo` will not hold duplicates of
copyright lines or SPDX expressions.
- click removed as dependency. Good old argparse from the library is
used instead.

Changed

- The `reuse --help` text has been tidied up a little bit.

Fixed

- Release date in change log fixed.
- The PyPI homepage now gets reStructuredText instead of Markdown.