Tweak positioning of delta bar during animation

Clicking at some location in the bar would sometimes result in the
delta-bar not being positioned completely behind the handle. This commit
positions the delta bar by using the position of the relevant handle,
rather than trying to work out the position using the value.
Update to jQuery 1.10.2 (was 1.7.1)
Improve positioning and movement of handles

Instead of trying to work out by how much the handle should overhang
("dangle" over) the edges of the bar, this is now determined by the
left- and right-margin on the handle element. Negative margins will
result in the handle overhanging the edges of the bar.

This has the effect of making rendering of handles more robust when the
width of the quinn element is set directly (instead of being constrained
by a parent element).
Slightly darken border on example code divs
Progressively enhance HTML inputs

Inputs (text, number, or range elements) can now be enhanced into Quinn
elements, with their attributes being used in place of providing options
when initializing the Quinn range.
Remove the broken annotated source docs
Improvements courtesy of JSLint