Redo button states

Redo button states

Trying to simplify our output here by revamping these selectors. We overcomplicated things by setting hover styles for nearly every state (disabled and active included), and we set them in the wrong order.

This commit does the following:

- Reorders states so disabled comes before active, thereby removing the need to set disabled-active styles.

- Removes all focus and hover styles from disabled states as those will naturally inherit from the default button state.

- Renamed `.open` to `.show` to fix dropdown toggle highlighting.

- Tweaked some indendation in the Sass.