Scale the entire chart

Hi,

It is useful for me to be able to "scale the entire chart":

Example:
If I am displaying the chart in a 200px square box, but I want to have C3 render it to a 400px square area with a scale of 0.5 (the formatting is slightly different: the graph is larger and the legend is smaller)

I have gotten it to work by applying the following code:

update `c3_chart_internal_fn.initWithData` and insert
`.style("transform", "scale("+config.data_scale+","+config.data_scale+")")` on line 257

update `c3_chart_internal_fn.getDefaultConfig = function () {` and insert
`data_scale: 1 ,` on line 1296

update `c3_chart_internal_fn.getCurrentWidth` and replace
`return config.size_width ? config.size_width : $$.getParentWidth();`
with
`return (config.size_width ? config.size_width : $$.getParentWidth())/config.data_scale;`

update `c3_chart_internal_fn.getCurrentHeight` and replace
`return h > 0 ? h : 320 / ($$.hasType('gauge') && !config.gauge_fullCircle ? 2 : 1);`
with
`return (h > 0 ? h : 320 / ($$.hasType('gauge') && !config.gauge_fullCircle ? 2 : 1))/config.data_scale;`

Note that my changes did not update/ alter the font size.. and if the idea is accepted, it may need to be done too.

Thanks!