Modin 0.10.0

This release contains significant amounts of improvements to the
maintainability of the code. Documentation was added for the low
level code at many levels.

Another key addition this release is the two major interface
additions: Spreadsheet and SQL.

Key Features and Updates
------------------------
* Many Documentation updates
* Stability and bugfixes
* Spreadsheet Interface
* SQL Interface
* Ray 1.4 support
* pandas 1.2.4 support
* Performance improvements
  * Improvements for XGBoost
  * Some groupby calls
  * map operations
* Metadata management improvements
* Improvements to Testing and CI
* pandas API ehancements
  * fillna
* Omnisci backend enhancements

Contributors this release
-------------------------

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

@YarShev
@anmyachev
@dchigarev
@krfricke
@tkeech1
@vnlitvinov
@btseytlin
@gshimansky
@prutskov
@todd-yu
@kvu35
@amyskov
@richardlin047
@igalink
@devin-petersohn