Modin 0.7.3 release notes

Bugfixes + Pandas Concordance (🐛 + 🐼)
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* DataFrame.drop_duplicates correctly identifies subset type now (718ae58d)
* Fix error in Groupby when grouping with multiple columns (776ae108)
* Update supported pandas version to 1.0.3 (588444fb)
* Fix numpy array assignment on empty dataframe (f763cea1)
* Add temporary fix for ray race condition (78395d96)
* Choosing depedencies for pip install modin[all] based on platform (c69f455c)
* Make DataFrame and Series constructor behavior match pandas (fa3bd55b)
* Assgning Series to an empty DataFrame is done correctly (362d20f2)
* Fix cases where read_json should fall back to pandas (670d56f3)
* Fix parquet file reading when file was written with pandas Index (8a4a3859)
* Fix internal APIs for read_gbq (bf437e75)
* Fix cases where read_json should fall back to pandas (670d56f3)
* Change ‘getitem_slice’ to ‘iloc’ implementation (8efca60f)
* Fix cases where read_json should fall back to pandas

New Functionality ✨
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* Add MODIN_CPUS env variable for command line CPU specification (745caf7c)
* Add implementation for Series.groupby (4b49f1ae) ⭐️
* Add broadcast_apply internally to apply functions (439b396f)
* Add parallel support for binary functions with Series other (79d639f1)

Code Quality + Testing 💯
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* Add cov flags to pytest.ini so coverage is always computed (#1132) (51f195f5)
* Update GitHub Actions to remove those tests run on TeamCity (9e6851ea)
* Remove dead code from PythonFrameManager (5dc904b6)
* Make query compiler base class a Python ABC. (e9b839a7)
* Deprecate Dask Delayed in favor of Dask Futures (7edfc489)
* Add Dask to coverage tests (1ea094b4)

Backend enhancements + Performance 🚀
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* Improve import performance and reduce sys.modules (68d377aa)

Documentation 📃
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* Add Windows Conda environment file for development on Windows machine. (8c56e1a6)
* Fix description of from_pandas method (1005b365)
* Fix description of some methods (3650a137)

Dependencies 🔗
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* Bump psutil from 5.4.8 to 5.6.6 (7f067677)
* Pin pyarrow to 0.16 until we can update interfaces internally (8fc5532b)
* Update Ray version to 0.8.4 (6d90c83b)

Contributors this release

The following users contributed code to Modin since the last release.

@YarShev (First time contributor) ⭐️
@anmyachev (First time contributor) ⭐️
@datapythonista (First time contributor) ⭐️
@gshimansky (Returning contributor) 🌟
@simon-mo (Maintainer)
@devin-petersohn (Maintainer)

🎉🎉 Thank you! 🎉🎉