I updated the doc with an example of a flex layout of 3 columns where the center column is specified as a `.col-xs-5` to show that other columns will resize no matter what the width of the center column.
Experienced bootstrap developers will expect to have to use an even number for the center column width when in reality any size will work.
I believe this is quite useful information and doesn't add too much to the docs.
Another option would be to make that initial example a `.col-xs-5` instead of a `.col-xs-6` to highlight this fact in the first place.
- Creates new flexbox grid Sass file in our docs assets
- Updates the Gruntfile to compile said new Sass file and minify the output
- Update notice on flexbox docs page for how it works
- Only enable compiled flexbox grid CSS in hosted docs site, not in dev (for easier and specific debugging of all flexbox features)
- Flexbox responsive behavior fixed with specific .col-{breakpoint} classes now added
- Dropped the make-col mixin in favor of a column-basics placeholder that we can extend across our grid infrastructure
- Updated docs to use required .col-xs-12 (as a safeguard for when folks enable flexbox mode--this isn't necessary in default grid mode)
- Update flexbox grid docs to include responsive docs, tweak some other bits too
