+Added some features to make it more easy to work with.
+fixed a small bug which prevented the items of interst from being
counted correctly.
+Added a simple implmementation of the sliding window which *should*
support querying over dates.  The interface has changed a bit, so I hope
it words.
+Added some basic debuging printout to make sure the program is working
as expected.
+Added a driver program which loads some data and enables querying over
the entire data set.