* feat: Col support `flex` prop
* update snapshot
* update doc
* row component use flex type by default
* revert grid flex layout doc
* remove float style
* remove doc old FAQ
* revert .make-row
* col style use flex and max-width
* remove useless Col style and imorove base doc for a single Col
* update snapshots
* fix flex mode pseudo
* update snapshots
* back to old flex mode demo gray background color
* set default col flex => 1 auto
* change grid about flex mode description
* update snapshots
* improve grid introduce and fix with gutter bug
* update snapshots
* remove version
