Reorder inputs to restore radiused border on the right side of the input-group
Add extra wrapper to fix overflow: hidden in firefox

The .input-group has display: table.  This appears to cause Firefox to
ignore the overflow: hidden.  This results in the file select dialog being
triggered by clicks anywhere in a large region above and/or to the left
of the file widget.
Adjust positioning of invisible file input for FF 3.5