Addition of a pull request format and testing stuff

[Eddio0141]

Problem with adding bunch of features are not all of them can work flawlessly with all unity features.
It's hard to know what broke which unity features across many versions from 3.4 to latest when adding in new stuff without proper testing.

So for every pull request, there has to be some rules on a template to ensure the added / modified UniTAS feature works across unity 3.4.0 ~ latest without issues.

This issue tracks:

• Way to test UniTAS properly in unity #223
• Adding pull request template #285