Option to control blank border on each side of the category axis?

Hi,

I can't figure out how to get rid of gap on each end of the X axis (before and after the first and last X values): http://i.imgur.com/TntkyC6.png

My code: http://jsfiddle.net/bz9mLome/

For example, Baidu's ECharts has a `boundaryGap` option which allows exactly that. I couldn't find anything similar in C3, so would appreciate any workarounds and also put in a feature request.

Thank you.