7.2.0 — really explicit col-* styles

7.0.0-alpha12 introduced the two new bugs (#11):

1. If col- is not at the start of a class name, like class=" col-md-6" or class="first-xs col-md-6", then it will mismatch the selector.
2. When using css-loader, [class=^col-] won't be exported, because css-loader's CSS Module only works with class name selector.

Since flexboxgrid2 used in react-flexbox-grid, we are responsible to their users, so we can't degrade their experience.

Now we reverted that selector and explicitly add paddings to all .col-* styles, thankfully to @jacargentina for his PR.