Tried redoing this in flexbox, but it falls apart really quickly. Any changes in height of the cells throws it all off since the rows become columns (and thus, content across columns cannot be equally sized). Rather than implement something with such glaring flaws, I'm nuking it outright.
- Renames .pos-f-t to .fixed-top, adds .fixed-bottom and .sticky-top
- Updates utilities Sass to be split across more files (one for position, sizing, and spacing)
- <progress> element didn't allow animation, labels overlaid, multiple bars, etc.
- Revamps CSS to use something more similar to v3's implementation
- Ditches variant mixin for `bg-` utils
- Rebuilds docs to match, including adding a new Height section for customizing that.
Only potential remaining todo is adding `.sr-only` instances to within the bar. Unsure if that's necessary.
- since we're column to start, need to set row.
- note that flex-direction cannot be inherited, so we have to set it twice.
- apply the horizontal padding again to .nav-link.
- remove the .nav-item styles (un-needed).
- remove previous .nav-link styles as they were un-nested and potentially problematic in old placement should someone mix more navs in here.
since we're no longer using the .nav as a base class, we need to bring over some base styles for redoing browser list styles and setting flex in motion.
also brings with it some .nav-link styling. we're still using this global class, but with this small modification for alignment of content in responsive modes.
- Overhauls the states, including the link/button variants, for list groups to better match how we handle .btn states.
- Moved the .list-group-item-action styles before the .list-group-item so that we don't have to do as much overriding.
- Removed the plain-hover-focus mixins from the disabled and active states since they're unnecessary.
- Added support for :active states on the .list-group-item-action variant (for the current click state).
- Removed the heading and text classes and variables since we can accomplish the same thing with utilities.
- Added support for :disabled on the .list-group-item-action as well since we can use those with button elements.
- Rearranged docs to reflect all the above changes.
- Reformatted some Sass variables.
