Rickshaw.Graph.RangeSlider.Preview supports millisecond zooming

Changed the domainScale interpolate function to d3.interpolateNumber
(vs. d3.interpolateRound) so that the RangeSlider Preview Window could
zoom into millisecond levels of precision (before it would only allow a
window of 1 second)
Fix #377: Ensure multi renderer consults it's sub renderers about how they perceive their domain
Merge pull request #378 from dwt/377_multi_renderer_domain_doesnt_call_sub_renderers_domain

Fix #377: Ensure multi renderer consults it's sub renderers about how th...
Merge pull request #372 from deldrid1/master

Rickshaw.Graph.RangeSlider.Preview supports millisecond zooming
Fix typo
Merge pull request #383 from mo/fix-typo

Fix typo