Publish an es6 module or default to es6 style module

[wmira]

At the moment we need to do import one at a time to prevent a whole import of the icon tree. We should export an es6 version to have it easier to use if users are using bundlers like webpack 2 that supports tree shaking

target:

import { someIcon1, someIcon 2} from 'react-icons-kit/es6/md'

The above works like

import { someIcon1 } from 'react-icons-kit/md/someIcon'
import { someIcon2 } from 'react-icons-kit/md/someIcon'