- added tickArray feature to allow arbitrary placement of ticks

I needed the ability to have the ticks be in arbitrary spots, not just increments.  I've added "tickArray" as an option.  If given it ignores "tickInterval" and displays only those ticks given.  "tickArray" should be an array of tick positions.  The label drawing still respects the "tickLabels" feature but ignores the tween option.

I haven't regenerated any of the dist files to go with this, so this commit only updates the labelled slider file and adds a test html page.

Cool widget.  Thanks for putting it out there.