Release 0.21.4 - bugfix release (choderalab#590)

* Updated release notes for version 0.21.4

* Updated notes with suggested corrections.

Release 0.21.3 changelog (choderalab#574)

* Improved changelog with suggestions.

Co-authored-by: Mike Henry <11765982+mikemhenry@users.noreply.github.com>

fix build badge for default branch change from master to main (choder…

…alab#552)

More streamlined context caches usage (choderalab#547)

* Removing context_cache kwargs. Users have to use instance attributes for context caches.
* Adding context cache attributes and examples in docstring.

Release 0.21.0 (choderalab#545)

* updated docs

* add all the context cache fixes

* Update docs/releasehistory.rst

Co-authored-by: Iván Pulido <ivanpulido@protonmail.com>

Co-authored-by: Iván Pulido <ivanpulido@protonmail.com>

Fix critical bug in which GPU contexts would fail to recognize mixed …

…precision was available choderalab#506

Remove leftover `six` imports and `xrange` see PR choderalab#504

Bugfix release

This release fixes several bugs and eliminates cython compiled acceleration of replica-exchange all-swap (replacing it with numba) to enable working release on conda-forge.

Merge pull request choderalab#469 from choderalab/update-neq-test

Update neq integrator tests to generate trajectory.

Merge pull request choderalab#451 from choderalab/fix-release

Another small fix to release notes