7.0.0-alpha12 — box-sizing and implicit col-* behaviour across all screen sizes

Two major features:

• box-sizing: border-box at .container to get rid of overfows (thanks @akronb, #7),
• implicit .col-* styles at all screensizes if presented at least one — no more col-xs-12 if you want just paddings!

- <div class="col-xs-12 col-md-6 col-xl-3"></div>
+ <div class="col-md-6 col-xl-3"></div>

Breaking changes

• box-sizing: border-box at .container

When stable?

If this release will not cause any bugs, we'll release stable 7.0.0 at 16 Nov.