There is no time performance comparison for small maps vs HashMaps

[Zteve]

Add a time performance measuring test; analogous to the memory usage tests currently there.

It would be nice to know if SmallMaps out-perform HashMaps for very small maps. If they do, where is the break-even point? This would be interesting from the HashMap point of view also.

While we're at it, some performance measures for creation of SmallMaps vs HashMaps would be good, too.