Review code for platform-specific file paths

[mcoles]

Linux users encounter friction because VizAlerts was developed and tested on Windows, and uses Windows conventions for filepaths.

Examples are several config file values:

https://github.com/tableau/VizAlerts/blob/master/config/vizalerts.yaml#L2 https://github.com/tableau/VizAlerts/blob/master/config/vizalerts.yaml#L5 https://github.com/tableau/VizAlerts/blob/master/config/vizalerts.yaml#L6

Here's one hard-coded in the executable script itself:

https://github.com/tableau/VizAlerts/blob/master/vizalerts.py#L84

We should do a search for all references to platform-specific paths and render them platform-agnostic. At the very least the config file should also be commented to provide instructions for Linux users.

Reference: https://community.tableau.com/s/question/0D58b00009WrPcNCAV/