Bump version to 2.0.0

Bump version to 1.6.5

* Properly package the `canonicaljson` module.

Bump to v1.6.2.

The v1.6.1 tag was created without having bumped the version in
`canonicaljson.py`. This means that installing from git tag will install
the package with the wrong version in its metadata. The 1.6.1 artefacts
uploaded to PyPI _did_ have the correct version; `pip install`ing
directly from the archive resulted in a consistent version number.

There are no other changes in v1.6.2.

Type annotations for canonicaljson (#49)

v1.6.0

Make frozendict an optional dependency, not mandatory.

Release 1.5.0

Version 1.4.0 released 2020-09-03

* Fix producing non-standard JSON for Infinity, -Infinity, and NaN. This could
  cause errors when encoding objects into canonical JSON that previously used to
  work, but were incompatible with JSON implementations in other languages.
* Use UTF-8 to fix ASCII encoding errors when data containing Unicode was
  attempted to be pretty-printed.

Version 1.3.0 released 2020-08-14

* The minimum version of simplejson was bumped to 3.14.0.
* Obsolete workaround for slow encoding of Unicode characters was removed.
* New APIs were added to iteratively encode JSON.