GitHub for Unity 1.2.1 - "Tailoring The Racoon Suit"

This release is a hotfix for an issue affecting Unity 2018.3.

It works around Unity issue 1113071, which causes the plugin to never initialize properly.

Fixes

• #990 - Initialization message constantly showing up in 2018.3
• #995 - Include *.mat files in .gitattributes
• #992 - Update the generated .gitignore file with the latest from https://github.com/github/gitignore (courtesy of @FurkanKambay!)