* Mention dropping of .checkbox/.radio
* copy edirts
- Dropped `.form-group-*` classes for simplicity's sake. Use `.form-control-*` classes instead now.
- Dropped `.help-block` and replaced it with `.form-text` for block-level help text. For inline help text and other flexible options, use utility classes like `.text-muted`.
- Dropped `.radio-inline` and `.checkbox-inline`.
+- Consolidated `.checkbox` and `.radio` into `.form-check` and the various `.form-check-*` classes.
- Horizontal forms overhauled:
- Dropped the `.form-horizontal` class requirement.
- `.form-group` no longer applies styles from the `.row` via mixin, so `.row` is now required for horizontal grid layouts (e.g., `<div class="form-group row">`).