People consistently confused about imports in showcase

[mcnuttandrew]

There have been a bunch of issues where folks have been trying to follow the showcase examples to a T, which leads them to use incorrect imports. I think someone should do a pass through the docs and make them as copy and pastable as possible. This might mean introducing a webpack name space (i think i'm using this term right) so that you can do things like

import {RadarChart} from 'react-vis'

and react-vis will point to the index of the library.