Modified method of evaluating the conditional intensity to take memory issues into consideration.  Now has a similar structure to linkages etc.
Updated validation call to allow a callback function between time slices - allowing incremental updates/dumping to disk.
Outside of this package, have experimented quite a lot with C++ implementations of the KDE.  Ultimate outcome is a VERY marginal speed increase - perhaps 10pct max.  Not worth the huge hassle of boost.python etc.  Suggests current KDE implementation is pretty good.
Added pickling callback to big Chicago validation.  Running now.