Brython-server

This release should address the issues outstanding since the 2.1.12 release from the summer of 2019. Specifically:

* Google Drive integration links should behave correctly when generating a share/link to a Github file.
* Shared/linked Google Drive files should behave as expected in incognito windows (provided the file is shared with unrestricted access).
* Support for the current latest version of Brython (3.8.9)
* The original pale yellow background color has been restored.
* The "credits" to Brython Server and Brython and corresponding links in the lower left corner of the page have been revised and now include their respective version numbers.
* The "credits" part of the console view has been simplified to make it easier to find your way back to the editor.
* The Javascript has been passed through the standardjs code linting and formatting tool and testing scripts have been updated to include this as a standard test.
* Support for using Travis CI for automated testing has been put in place. Initially, this is only includes Black formatting for Python, Python linting, and standardjs for the Javascript. This support will enable additional unit testing in the future.
* Repository README has been updated to include information on setting up and using a development environment.
* In the course of preparing this release, the entire release process was tested from the ground up and some minor problems were uncovered and fixed.

Add option to save to Drive Root or select a folder.

Google drive "save" button requires the user to select a folder before saving.

Update to use the latest release of Brython (3.7.4)
Update to use ggame 1.0.11 (which supports Brytyon 3.7.4)
Update to support Google Drive UI integration.

Updates to support deployment on the Google App Engine:
* Restoration of Redis for caching and session data
* Support for Redis instances on different machines by introducing appropriate environment variables.
* Brython must be installed prior to releasing to pypi. The full install cannot be performed solely with pip3 during deployment.
* Deployable either to a conventional host or to Google App Engine (requires Memorystore/Redis, VCP and VCP connector).
* Deployment to GAE requires only an app.yaml and requirements.txt file.