Use 100% width for rst-footer-buttons

[Blendify]

This fixes the buttons from jumping around on small pages/ resizing

[ericholscher]

Is there an example that this fixes? Would be good to understand a bit more.

[Blendify]

Here is an example

[Blendify]

To fix this we did:

.rst-footer-buttons::before , .rst-footer-buttons::after{
	width: 100%;
}

I assume this does the same thing; just started using sass today.

[Blendify]

planing changes here

[ericholscher]

Seems like a reasonable fix, thanks. I'll take a look and merge it next week.

[Blendify]

See #370