Understandable error messages from uglifyjs
add grunt, see more in README.md about how to use intstall and use grunt
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
```

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Add opt-in scatter point color override.
FIxing bug in line.js.
Merge branch 'master' of https://github.com/novus/nvd3

Conflicts:
	nv.d3.min.js
Adding historical bar chart code.
ran make on nv.d3.js
Updated several charts so that the showXAxis, showYAxis and rightAlignYAxis options are available for use.
rebuilding nv.d3.js and minified version.
added colorbrewer.js to lib
Merge branch 'master' of https://github.com/novus/nvd3 into development
Merge branch 'development' of https://github.com/novus/nvd3 into development
ran make
Merge branch 'grunt' of https://github.com/lihongxun945/nvd3 into lihongxun945-grunt

Conflicts:
	nv.d3.min.js
fixed a merge conflict. No change to master code, so this commit is not tagged
expose x-axis group spacing in multibar
Merge branch 'master' of https://github.com/novus/nvd3

Conflicts:
	examples/historicalBarChart.html
	nv.d3.js
	nv.d3.min.js
	src/models/historicalBarChart.js
	src/nv.d3.css
Adding PNG image to show what a sample line chart looks like. For the WIKI documentation.
Fixed two stacked area chart issues:
1. When in expanded view in stacked area chart, if there is missing data (zero data), 'holes' will be displayed in the chart where data is missing.
2. Tooltips used to be disabled if the stacked area showed values less than zero. This functionality has been disabled.