Add different environment

[ai]

Config:

[development]
last 1 browser

[production]
last 4 versions

pckage.json:

"browserslist": {
  "development": ["last 1 browser"],
  "production": ["last 4 browser"]
}

Based on Create React App discuss: facebook/create-react-app#892

[ai]

Do we need to add object support to browserslist(browsers) argument?

I think we could ignore it. If you set it manually, you can use JS to use different arrays for dev/prod.

[ai]

Finished by #88 and #89