removed the multiline chart stuff from WIPs since this is pretty stable.
Fix issue #92
Fix issue #88 - voronoi rollovers instead of rects
Fix issue #88 - cleanup
Fix issue #88 - voronoi for multi, rect for single

Voronoi overlays for single line charts made the mouse-overing slightly
awkward, this makes rects the default for single line charts and
voronoi the default for multi-line ones.
Cleanup
Merge branch 'master' into gh-pages