Add scrolling to modal acceptance frame, in case of overflow. Modaless handled by browser scrolling.
Fix for long metadta in the badge acceptance flow.

It's important to show all the data at that stage,
so the fix doesn't truncate anything, and forces
long urls or other unbroken strings of text to wrap.

The LESS has some comments on what to do if that's
not the desired behavior.
Merge pull request #753 from stenington/685-metadata-overflow

Badge metadata overflow in badge acceptance [closes #685]