Add CONTRIBUTING.md guide for future contributors

[mnquintana]

We should add a Contributing guide (generally CONTRIBUTING.<text extension>) to set out our guidelines for how we want future external contributions to work. It should contain (at least) the following stuff:

• Code style / conventions
• "Getting Started" guide for newbie contributors (note: different from the current Getting Started section in the README which is geared towards users)
• Guidelines for reporting bugs
• Community code of conduct
• Guidelines for opening PRs
• Dev environment setup
• Running tests
• Guidelines for improving documentation
• Testing policy (should all the tests pass in a PR? probably!)
• Contribution workflow
  • ie. 1) Check issues list / open PRs first; 2) Check next version milestones; 3) Write tests; 4) Make them pass; 5) Refactor; 6) Open PR; or something like that

(We might end up having to move some info from the Readme to Contributing - that's okay)

As a sweet bonus, GitHub automatically adds a link to a repo's CONTRIBUTING file if it exists as a message at the top of every PR and issue made.

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Here are some good examples of Contributing guides from other projects:

• Angular
• Leaflet
• Gulp
• Ghost
• jQuery
• Atom
• Brackets
• Rails (really intensive)
• Bower
• http://contributor-covenant.org/

[orenyk]

This is a great idea! I'm not sure if it will happen in the next month or so but we should definitely get it written up before Reservatons starts coasting. Adding to Pre-Export.

[squidgetx]

implying we have a convention for code style

[mnquintana]

@squidgetx lol we will choose one