Clarify Contribution style requirements

Add examples to give clear guidance (and a reminder),
of commit message style requirements.

CONTRIBUTING.md

@@ -1,7 +1,30 @@
+# Commit message style
 When submitting changes via a pull request, or any other means, please format commit messages using ["50/72" guidelines, as suggested by Tim Pope](https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html).
 
-Summary:
+## Summary:
 - Maximum 50 character first "title" line, written as a capitalized [imperative sentence](http://examples.yourdictionary.com/imperative-sentence-examples.html).
 - If necessary, more detailed explanatory paragraphs following a blank line, with lines wrapped at maximum 72 characters.
 - If used, bullet points have a "hanging indent".
 
+## Example 1:
+```
+Make state variables used by pollButtons() public
+
+The variables currentButtonState and previousButtonState used by
+pollButtons(), justPressed() and justReleased() have been made public.
+This allows them to be manipulated if circumstances require it.
+
+The documentation added for previousButtonState includes an example.
+```
+
+## Example 2:
+```
+Refactor text code and add char size functions
+
+- Functions write() and drawChar() were refactored for smaller code
+  size and to make text wrapping operate more like what would normally
+  be expected.
+
+- A new flag variable, textRaw, has been added, along with functions
+  setTextRawMode() and getTextRawMode() to set and read it.
+```