Update nvd3 d3 dependency to ~, so no conflicts with packages who also require d3 at a newer 3.3 version.
Merge pull request #376 from DavidSouther/d3_dependency_update

Update nvd3 d3 dependency to ~
Made a fix to calcApproxTextWidth, to fix bug on IE9.
ran grunt production to make nv.d3.min.css. Also tagging for version 1.1.15b
updated README
Finish previously incomplete pull request #263
Fix scatter single point class removal

Once a scatter is rendered with a single point, it would keep this
setting even on the updates where more points might have appeared. Redo
the single point detection each time and set the class accordingly.
Fix legend texts width computation