Add CONTRIBUTING.md

Add Learn more section

Fix egghead.io link

Highlight buttons, controls and badges

Bold the buttons, controls and badges

Correct step sequences

CONTRIBUTING.md

@@ -0,0 +1,104 @@
+# Contributing
+
+**Are you wondering how you can get started?** You can learn how from this *free* series
+[How to Contribute to an Open Source Project on GitHub](https://egghead.io/series/how-to-contribute-to-an-open-source-project-on-github).
+
+## Prerequisites
+
+1. A GitHub project in which you have access
+2. A text editor or IDE (integrated development environment)
+3. Basic knowledge of the command line in a terminal session
+4. [`git`](https://git-scm.com/)
+5. [`SSH key`](https://help.github.com/articles/connecting-to-github-with-ssh/)
+
+## How to submit a Pull Request (aka PR)
+
+1. Click the _**Fork**_ button in the top right to copy the repo to your own GitHub project.
+2. Open a terminal and clone your forked project locally:
+```bash
+$ git clone git@github.com:your-project-name/chromebrew.git && cd chromebrew
+```
+3. Create a branch for your PR:
+```bash
+$ git checkout -b update-cool-package
+```
+4. Add, edit or delete the file(s) you would like to change and save.
+5. Test your changes!  See steps 7 through 11 in the `How to test a pending PR from another contributor` section below.
+6. Stage your changes:
+```bash
+$ git add -A
+```
+7. Review your changes:
+```bash
+$ git diff --staged
+```
+8. Correct your changes and repeat steps 4 through 7, if necessary.
+9. Commit your changes:
+```bash
+$ git commit -m "Add some awesome change to cool package"
+```
+10. Push your changes:
+```bash
+$ git push origin update-cool-package
+```
+11. Visit your project page in the browser: `https://github.com/your-project-name/chromebrew`
+12. Click the _**New pull request**_ button next to the _**Branch:**_ selector drop-down.
+13. Select your branch name from the _**compare:**_ selector drop-down on the right.
+14. Scroll down and review your changes.
+15. Click the _**Create pull request**_ button.
+16. Add a short description of your change.
+17. Click the _**Create pull request**_ button.
+
+## How to test a pending PR from another contributor
+
+1. Open the PR of interest.
+2. Next to the green _**Open**_ badge, you should see something similar to:
+```
+contributor-name wants to merge 1 commit into skycocker:master from contributor-name:update-cool-package
+```
+3. On the far right, take note of _**contributor-name:update-cool-package**_.  This is the PR contributor along with the branch they want to merge.
+4. Open a terminal, change to your cloned chromebrew directory and execute:
+```bash
+$ git remote add contributor-name git@github.com:contributor-name/chromebrew.git
+```
+5. Fetch their branches:
+```bash
+$ git fetch contributor-name
+```
+6. Checkout their branch:
+```bash
+$ git checkout update-cool-package
+```
+7. If the requested change is a package:
+```bash
+$ cp packages/cool_package.rb /usr/local/lib/crew/packages/
+```
+8. Test the new or updated package:
+```bash
+$ crew upgrade cool_package
+```
+9. Examine the files to see if everything installed as expected:
+```bash
+$ crew files cool_package
+```
+10. Run some tests on executables, if applicable:
+```bash
+$ cool_package --version
+$ cool_package --help
+$ cool_package --some-other-option
+```
+11. To see if this package is a dependency for another package, execute:
+```bash
+$ grep "depends_on 'cool_package'" packages/*.rb
+```
+and, just in case:
+```bash
+$ grep 'depends_on "cool_package"' packages/*.rb
+```
+If the package is a dependency for another package, test commands of the other package, if possible, to see if they were affected in any way.
+
+12. Visit the PR and add a comment suggesting any changes or mark it RTBC if everything looks good.
+
+## Learn more
+
+- Visit the [wiki](https://github.com/skycocker/chromebrew/wiki)