Updating CONTRIBUTING.md (#2355)

* Describe how to test in CONTRIBUTING.mD

* Adding a way to run js test in CONTRIBUTING.md

* Move 'hacking on noms' contents to CONTRIBUTING.md

CONTRIBUTING.md

@@ -1,7 +1,34 @@
-Noms is open source software, licensed under the [Apache License, Version 2.0]().
+Contributing to Noms
+====================
 
-Due to legal reasons, all contributors must sign a contributor license
-agreement, either for an
-[individual](http://noms.io/ca_individual.html) or
-[corporation](http://noms.io/ca_corporation.html), before a
-pull request can be accepted.
+## License
+
+Noms is open source software, licensed under the [Apache License, Version 2.0](LICENSE).
+
+## Contributing code
+
+Due to legal reasons, all contributors must sign a contributor license agreement, either for an [individual](http://noms.io/ca_individual.html) or [corporation](http://noms.io/ca_corporation.html), before a pull request can be accepted.
+
+## Languages
+
+* Use Python, JS, or Go.
+* Shell script is not allowed.
+
+## Coding style
+
+* JS follows the [Airbnb Style Guide](https://github.com/airbnb/javascript)
+* Go uses gofmt, advisable to hook into your editor
+* Tag PRs with either "toward: #<bug>" or "fixes: #<bug>" to help establish context for why a change is happening
+
+## Running the tests
+
+You can use `go test` command, e.g:
+
+* `go test $(go list ./... | grep -v /vendor/)` should run every tests except from vendor packages.
+
+For JS code, We have a python script to run all js tests.
+
+* `python tools/run-all-js-tests.py`
+
+## Recommended Chrome extensions
+* Hides generated (Go) files from GitHub pull requests: [GitHub PR gen hider](https://chrome.google.com/webstore/detail/mhemmopgidccpkibohejfhlbkggdcmhf).