Define Home For Developer Contribution Guidelines

Goal: Documented how one can contribute to this repo including patterns and best practices we follow

Acceptance Criteria

There exists a CONTRIBUTING.md file in the root of the repo that contains the following:
- Table of contents section with entries for each of below sections
- Welcome section that includes purpose of this product
- Environment details. Step-by-step guide on how to setup local development environment
- Testing. Our automated and manual testing expectations for new features and bugfixes
- How to create a new issue. Define what labels should be placed on what issues
- Guidance on picking up an issue to contribute
  - include guidance on branch and commit naming convention
  - branch should include issue number
  - commit message should be 'X: ' where X is the issue number and message is in the imperative tense following how to write a good git commit
Update the README to link to this for all contributing related content
Look to other open-source repos and resources like this one covering atom for inspiration and ideas

jacketattack / blackjack-is-fun