Implemented field `style` for both items and groups, to set a custom style for individual items.
Allowed for negative bar charts
Replaced all `arr instanceof Array` with `Array.isArray(arr)`
initial hiding of times, currently only one time is allowed
working arrays to hide, fixed zoom, fixed pinch, made seperate volatile object for dynamic date support.
Fixed #331: onclick events in items not working.
almost working hiddenDates, generic and specific. Only start times now
Merge remote-tracking branch 'origin/develop' into develop

Conflicts:
	dist/vis.js
fully working hiddenDates! woohoo!
Docs and history for hiddenDates
added oldWidth and oldHeight to resize event
Merge branch 'develop' into quickFeatures

Conflicts:
	dist/vis.js
	dist/vis.map
	dist/vis.min.js
	lib/timeline/Core.js