Added a note about new props, methods to README.md#Developing

Author: fmoo

README.md

@@ -285,6 +285,7 @@ Once that's done, running the tests is easy with `gulp`:
 Basically, fork the repository and send a pull request.  It can be difficult to review these, so
 here are some general rules to follow for getting your PR accepted more quickly:
 
+- All new properties and exposed component function should be documented in the README.md
 - Break your changes into smaller, easy to understand commits.
 - Send separate PRs for each commit when possible.
 - Feel free to rebase, merge, and rewrite commits to make them more readible.