FLUID-5276: Updating styling.
Merge remote-tracking branch 'simonbates/FLUID-5276' into FLUID-5276
FLUID-5276: Tweaked styling. Merged simonbates' changes.
FLUID-5276: Added fl-demoMenu-hidden visibility class.
FLUID-5276: Added position:fixed to the demoMenu position so it remains in place when viewport is scrolled.
FLUID-5276: Added max-height to the demoMenu container so that a vertical scrollbar would appear if height of viewport can not fit all content.