Presence of col-6 and col4 in html prevents proper stacking at small screen widths

Problem/Motivation

Column layouts created using the module do not stack at small breakpoints.

Steps to reproduce

Add a 2 or 3 column layout in a text area.
Save and view.
View at phone size.
Columns are still present vertically with squished text.

Proposed resolution

The presence of the col-6 (2 column) and col-4 (3 column) Override the col-sm-* and col-md-* classes in the div.
Removing these classes allows proper functionality.

Remaining tasks

Remove col-6 and col-4 classes from the __template__ divs in `js/widgerbootstrap/pligin.es6.js`