Update reference syntax in contributing docs

CONTRIBUTING.md

@@ -66,8 +66,9 @@ in the proper package's repository.
 
 * Use [TomDoc](http://tomdoc.org).
 * Use [Markdown](https://daringfireball.net/projects/markdown).
-* Reference classes with `{ClassName}` style notation.
-* Reference methods with `{ClassName.methodName}` style notation.
+* Reference classes with `{ClassName}`.
+* Reference instance methods with `{ClassName::methodName}`.
+* Reference class methods with `{ClassName.methodName}`.
 * Delegate to comments elsewhere with `{Delegates to: ClassName.methodName}`
   style notation.