Use simplejson if avail & do not sort keys unless debugging
Change deepcopy to shallow dict copy.

The deep copy operation is very expensive; particle generation performance is
30% faster with this one change.

It's also unecessary because all values in self.contents are immutable, hence
it's impossible for a change to the copy to affect the original.

If there were a mutable object in self.contents, then the above may no longer
be true.
eliminate expensive test
Removed cruft

Those lines had no effect.
Merge pull request #85 from n1ywb/driver_perf

Instrument Driver Performance Enhancements