Group as much as possible

Currently grouping requires at least 3 consecutive elements with common attributes. This leads to outputs like
<g stroke-width=".5">
<path d=.../>
</g>
<g stroke-width=".5">
<path d=.../>
</g>
if there are only 2 consecutive elements, that is, they are not grouped. This is obviously not optimal.
It would be advantageous to group even two elements if they have the same attributes. Or, better, always try to group >=2 elements, but accept the result only if it is shorter than the original code.