message: add FLEX system props, re-export system()
diff: @@ -2,6 +2,8 @@ import styled from 'react-emotion'
  import {compose} from 'ramda'
  import * as system from 'styled-system'
  +export default from 'system-components/emotion'
  +
  export const COMMON = ['color', 'space']
  export const TYPOGRAPHY = COMMON.concat('fontFamily', 'fontWeight', 'lineHeight')
  @@ -23,6 +25,20 @@ export const LAYOUT = COMMON.concat(
  export const POSITION = ['position', 'zIndex', 'top', 'right', 'bottom', 'left']
  +export const FLEX = COMMON.concat(
  + LAYOUT, // includes display
  + 'alignItems',
  + 'justifyContent',
  + 'flexWrap',
  + 'flexDirection',
  + 'flex',
  + 'alignContent',
  + 'justifySelf',
  + 'alignSelf',
  + 'order',
  + 'flexBasis'
  +)
  +
  export function getSystemProps(props) {
  const unique = props.filter((p, i, a) => a.indexOf(p) === i)
  return unique.map(prop => {
  