default props on xs, sm, md, lg

[Eduardo Ibacache Rodriguez]

You should have default value to 12 on all sizes, else you need to write all the props all the time.

<Col lg={6}>foo</Col>

This should automatically give you xs, sm, md = 12.

How it is today, the Col becomes a div with inline-block on the not set props, and it looks strange when expecting responsive layout.

[Javier Castro]

@eduardoinnorway try https://jacargentina.github.io/react-flexbox-grid/ for this feature