Fix/update dependencies

[privateOmega]

Hi @WaldoJeffers ,

I use dc.js in react and wrote code to generate graphs imperatively, but I wish to use a wrapper library like yours to use it in react in the future, so I thought of restarting development on this project and hopefully maintain it in the future. As a first step, I have updated the dependencies in the library and will do the crucial development on it soon, but I got stuck in the first step itself for past 2 days, hopefully you can help me out.

• [x] update react, react-dom and fix up issues related to it.
• [x] update webpack, babel and associated dependencies.
• [x] update other dev dependencies.
• [ ] update d3.js, crossfilter2 and dc.js packages.

This is the issue

utils.js:27 Uncaught TypeError: Super expression must either be null or a function
    at _inherits (utils.js:27)
    at eval (utils.js:80)
    at eval (utils.js:114)
    at eval (utils.js:48)
    at Object.decorateConstructor (bar-chart.js:27)
    at Object.decorateClass (bar-chart.js:27)
    at _decorate (bar-chart.js:25)
    at eval (bar-chart.js:60)
    at Module../src/charts/bar-chart.js (bundle.js:896)
    at __webpack_require__ (bundle.js:20)

[privateOmega]

just noticed that I forgot to upgrade d3, crossfilter and dc modules. will upgrade them as soon as the current issue is fixed.