Dql

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* Fix: Issue with missing dependency (typing_extensions) made apparent by python 3.9
* Added: Run tests with python 3.9
* Chore: general cleanup & lint fixes
* Chore: removing travis-ci; adding github workflows
* Added: `clear` & `cls` commands.
* Updated: clear, cls, exit commands are no longer tracked in history.

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* Feature: Retain query history across sessions. (40)
* Fix: Cannot count(*) on an index (37)
* Fix: Saving data to some file formats was failing
* Fix: Constraint functions accept quoted field names (36)
* Chore: Updated config for Dynamo Local to install dependency within project root.

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* Bug fix: Fixed ZeroDivisionError with ls on On-Demand tables (32)
* Added: ls command accepts glob patterns (30)
* Added: Better error handling and display. (28)
* Added: Standard error handling for execution with ``-c`` option. (28)
* Added: Keyboard interrupts will print spooky emojis. (28)
* Added: ``--json`` argument for use with ``-c`` to format results as JSON
* Chore: General Dev Env & CI updates for easier development. (27)

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* Bug fix: Encoding errors for some SAVE file formats

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* Bug fix: Proper throttling in Python 3

Dropping support for python 3.4

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* Use python-future instead of six as compatibility library
* Now distributing a wheel package
* Bug fix: Confirmation prompts crash on Python 2