Viewport Sizing is Inconsistent (col-sm vs visible-sm)

Created by: mbleigh

With Bootstrap 3 RC1, the sm keyword is used in an inconsistent manner. When referring to column sizes, it means "tablet sized." When referring to hide/show responsive classes it means "phone sized." My recommendation would be to rename all of the col-sm-X classes to be col-md-X classes.

This would solve the inconsistency while still advocating "mobile-first" and leaving the mobile columns un-prefixed.