Add development documentation

[ariesshrimp]

It would be nice to include a few paragraphs about development and the PR process. For example:

1. How do you do a dry run of your branch? Do you need to plug in a device to test against for any changes? What is the expected behavior?
2. How are tests written? How are they run? What's the minimum requirement for a satisfactory PR? Are including unit tests a requirement for a PR?
3. Who can click a PR approval? Just @chalkers? Anyone involved in the project? Should you ever approve your own PR, even if it's possible?
4. Is there any CI or other process oriented stuff developers need to be aware of?
5. Is there anything missing from the official repo that a developer would need to add / get in order to fully test their branch? For example, any private configuration required?
6. How should linting be done? What do you need to know about jshint to properly lint your branches?