Check if windowResize argument is undefined

When loading nv3d without creating a chart, ```nv.utils.windowResize``` is called somewhere with an undefined argument, so we should check if it is undefined and not try to replace the old event handler, otherwise every resize event generates an error because ```fun``` is undefined.

I was able to produce  by including the following libs and triggering onresize events.

```
nvd3/lib/d3.v2.js
nvd3/src/core.js
nvd3/src/tooltip.js
nvd3/src/utils.js
nvd3/src/models/lineWithFocusChart.js
nvd3/src/models/legend.js
nvd3/src/models/axis.js
nvd3/src/models/line.js
nvd3/src/models/scatter.js
```

Sponsored-by: CentroNet Marketing
expose x-axis group spacing in multibar
correcting bug on heigth and width property accessors of stackedAreaChart
add brushExtent to chart to enable the ability to set default focus range.

There is a brushExtent when init, so I guess maybe you guys just forgot to put the public function available.
use style text-anchor vs attribute to maintain consistency with d3: https://github.com/mbostock/d3/blob/master/src/svg/axis.js#L69
Use style text-anchor to properly rotate ticks.
Added type check for console.log to prevent IE8+modernizr issues
Merge branch 'master' of https://github.com/fskreuz/nvd3 into master-patched
Merge branch 'textanchor_style' of https://github.com/dimagi/nvd3 into master-patched
Merge branch 'patch-1' of https://github.com/tubaxenor/nvd3 into master-patched
Merge branch 'master' of https://github.com/luizlaydner/nvd3 into master-patched
Merge branch 'group_spacing' of https://github.com/dimagi/nvd3 into master-patched
Merge branch 'master' of https://github.com/CentroNet-Marketing/nvd3 into master-patched
Removed a line from multibar chart that was referencing undefined variable
'singlePoint'.
Removed a line from multibar chart that was referencing undefined variable
'singlePoint'.
Fixing issue in multibarChart where the axisLabel was being
rotated along with the xAxis tick labels, when rotateLabels
was set.
added classing to links in indentedTree
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
fix to previous fix