Temporarily(?) kill flow-ui-regressive

Dear Shahyar,
I know you have much love for flow-ui-regressive
but please help me remove it for the time being.

I ask, since it doesn't seem to be winning much love from the
design team (Brandon, Jared, May) I really think we should remove it
from Flow until we have more consensus.

It makes mobile moving to mw-ui-button a little harder (it seems to be closely
tied to the IE6 styling via [class].

I think it is the kind of big design change that we should make as a group and put
into core not in our own extension.

If you love something, set it free.
If it comes back, it's yours.
If it does not come back, it was never meant to be.

<3 Jon

Change-Id: I709f6784ecb4eb6c09ca406b1370a20f39b26650
Merge "Temporarily(?) kill flow-ui-regressive"