expose x-axis group spacing in multibar
Removed a line from multibar chart that was referencing undefined variable
'singlePoint'.
Merge remote-tracking branch 'origin/development' into development

Conflicts:
	nv.d3.min.js
Merge branch 'group_spacing' of https://github.com/dimagi/nvd3 into development

Conflicts:
	src/models/multiBar.js