Discussion: Link to reasons/discussions on tests

[minthemiddle]

• tlint is fantastic to follow best practices
• For learning it would be even more useful, if there was a linked why? for each test
• These could be links to discussions or articles
• For example I could not easily find an explanation for NoMethodVisibilityInTestsTest

[loganhenson]

I love this idea!

Some of these are from in person discussions though, and will have to be reconstructed.

I am open to PRs that add reasoning to the lint names in the readme, and will try to extract the discussions where I can from the tighten notes there!

For NoMethodVisibilityInTestsTest, I believe the primary point was in a standard PhpUnit suite the test method visibility is redundant (you usually aren't new-ing up PhpUnit class instances).

[loganhenson]

We are adding to the readme incrementally as discussion comes up or is revisited 👍