Stacked fraction, animated rainbow span, lined paper

Additional demos:

• setFontFeatureSettings()
• Rainbow span, animated
• Lined paper

Initial release

Companion app for my Advanced Android TextView talk, demostrating:

• Animated CompoundDrawable
• Text shadow
• Custom font
• Gradient text
• Patterned text
• HTML.fromHtml()
• Styled string
• AlignmentSpan
• ClickableSpan
• Emoji