math-with-slack windows executable support

This is a beta release of math-with-slack 0.4.1 that mainly aims to provide support for Windows environment without Python support. Other platform users are welcomed to use the script downloaded in this release, but are also encouraged to use the latest script provided in the source repo. This release includes

• math-with-slack.exe, which is a ready-to-go executable of math-with-slack.py for Windows created by pyinstaller. We expect the executable to work out of the box (i.e. double click and go), and if command line arguments are necessary (e.g. for providing path to Slack installation), one can also execute the math-with-slack.exe through Windows command prompt with necessary arguments are desired (see README.md of the source repo).
• the original math-with-slack.py script