WIP: Contributing guidelines. (refs #82)

WIP, so [skip ci]
Flesh out contributing guidelines (Resolves #166) [ci skip]
Remove "Feature Requests" section for now
Update the protip based on feedback

Uses a block quote and doesn't mention the `rake install` step
Update CONTRIBUTING.md based on feedback
Update README to point to contributing guidelines
Update CONTRIBUTING.md based on feedback [ci skip]
Update CONTRIBUTING.md based on feedback
Move the start a branch section to Making Changes
Merge pull request #183 from MaxGabriel/addContributingGuidelines

Add contributing guidelines