reduce touchend threshold  3.0 -> 5.0
don't process touchevents if more than one touch

...because right now it looks really weird, like when
you pinch to zoom etc.  see how usedOneFinger is used in this diff
put some pointing fingers/buttons in demo.html
add `active` to first slide to remove a flicker
fix some vertical scroll/pan UI weirdness
add android only-one-touchmove-bug workaround
touch for slide isnt working when zoomed in