Removed Chrome from automation, added Firefox, other fixes like virtualenv

[elulcao]

Hello all,

I created this PR, to refresh some dependencies that could be a problem in some cases, like using Chrome instead of Firefox. I verified the changes in virtualBox (ubuntu, Windows) and my local macOS.

Subject: Removed Chrome from automation, added Firefox, other fixes Problem: Chrome has been deprecated in favor of FireFox, because of the chance to hide extensions.

Solution: Changed Chrome to Firefox. Generalized start.sh to be usable by Unix-Like OS like macOS and Linux. Now the install.sh [bat] creates a virtualenv for installing instaPy and depends. With this change, InstaPy user will be able to isolate the *.py files from their local and the ones consumed by InstaPy. Used black to format the *.py files like the main InstaPy repo. Added .github directory for templates and stale.yml README updated with minor examples and references.