Update release date for v1.8.1 (#454)

Update release date for v1.8.1 in changelog.

Changelog entry for v1.8.0 (#413)

Add the updates to the changelog, tweaks to the README, and link to new
docs version.

Add changelog entry for v1.7.0 (#361)

Minor version that introduces some deprecations and couple of new
features.

Changelog entry for v1.6.1 (#320)

Minor release to include a small fix to make_xarray_grid

Add changelog entry for v1.6.0 (#316)

Changelog entry for v1.5.0 (#271)

Includes the new cross-validators and fixes to our base classes to
accommodate Harmonica.

Changelog entry for v1.4.0 (#248)

New minor release with new features and bug fixes. No breaking changes
or deprecations.

Add changelog entry for v1.3.0 (#223)

Changelog entry for 1.2.0 (#197)

Create a changelog entry and update the authors file to include
@santisoler

Add changelog for 1.1.0 (#152)

Created a changelog for the new 1.1.0 release with Zenodo DOI.
Updated the authors list and made it alphabetical by last name.
Updated install instructions to be clearer what numba and pykdtree do.