fixed a typo or two in Contributing section

[rfrancis]

Before submitting a pull request, please make sure the following is done:

• Fork the repository and create your branch from master.
• [NA] If you've added code that should be tested, add tests!
• [NA] Ensure the test suite passes.
• [NA] Format your code with ShellCheck.
• Include a human-readable description of what the pull request is trying to accomplish.
• [NA] Steps for the reviewer(s) on how they can manually QA the changes.
• [NA] Have a fixes #XX reference to the issue that this pull request fixes.

[rfrancis]

Go go gadget OCD! I kept seeing that line and rather than just report it, I figured I was pretty sure I knew what it meant to say. Hopefully.

[karbassi]

Thanks @rfrancis for the great PR.