Add redrawOnResize flag (off by default) to allow resizing

This update adds `redrawOnResize` to the options for DataMap; if enabled, a full redraw of the map is performed when the window is resized.
I think a better approach for setting this event handler is using `d3.select` and `.on` for events, like:
```js
d3.select(window).on('resize', function() {
//...
});
```

That way we don't have to worry about `existingOnResize`, or creating any other potential issues on the injecting website.