Merge pull request #45 from RaymondChao/ZSS-725

Feature ZSS-725: Provide a richtext editor for inline cell styles
ZSS-753 Cannot undo setRichText()
ZSS-754 The method Range.setValidation() doesn't have annotation @since 3.5.0
fine tune.
minor fix ZSS-725: hyperlink, strikethrough, superscript and subscript issues with RTF