Update React to v16

[zaki-yama]

ref. #290

[zaki-yama]

@stomita
Sorry for telling you after merged.

I found 2 problems when starting Storybook:

1. The following warnings occurs.

setDefaults is deprecated. Instead, you can pass options into withInfo(options) directly, or use the info parameter.

Passing stories directly into withInfo() is deprecated, instead use addDecorator(withInfo) and pass options with the 'info' parameter

It's because I updated the Storybook and its addons' version.
We should deal with later.

2. Some component raises propTypes error.
   ex. http://localhost:9001/?selectedKind=ButtonGroup&selectedStory=Inverse&full=0&addons=1&stories=1&panelRight=0&addonPanel=storybook%2Factions%2Factions-panel

Warning: Failed prop type: Invalid prop `type` of value `icon-border-inverse` supplied to `Button`, expected one of ["neutral","brand","destructive","inverse","icon","icon-bare","icon-container","icon-inverse","icon-more","icon-border","icon-border-filled"].

It also occurs in master branch, too.
I can deal with, but I can also ignore this because propTypes will be unnecessary after migrating to TypeScript.

[stomita]

@zaki-yama ok these problems seem better to be handled in different PR. The proptype check could be ignored as it might not be so correct and would be replaced later by TS typecheck.

[zaki-yama]

@stomita
Sure. Thank you.