=flex($justify: space-between, $alignItem: initial)
  display: -webkit-box      /* OLD - iOS 6-, Safari 3.1-6 */
  display: -moz-box         /* OLD - Firefox 19- (buggy but mostly works) */
  display: -ms-flexbox      /* TWEENER - IE 10 */
  display: -webkit-flex     /* NEW - Chrome */
  display: flex



  -moz-justify-content: $justify
  -ms-justify-content: $justify
  -webkit-justify-content: $justify
  justify-content: $justify

  -moz-align-items: $alignItem
  -ms-align-items: $alignItem
  -webkit-align-items: $alignItem
  align-items: $alignItem

=flex-rows
  +flex-wrap(wrap)
  +flex-direction(row)
  +flex-flow(row wrap)