Update Babel to 7.x

[dominik-zeglen]

I think it would be beneficial to update Babel to 7.x version - especially for <> tag support (React.Fragment) and keeping dependencies always up to date.

[bebraw]

Yeah, agreed. I would say the right time to update is when they go stable with it. Better leave this open till then.

[bebraw]

It's stable now. PR welcome (unless I get to it first).