#12 Histogram should support multipass run

[Charles Fry]

The Histogram class currently insists on using a cache
to determine bucket sizes, if they are not specified
explicitely. It would be nice to have an option of
using a two-pass algorithm rather than a cache, where
the first pass found the max and min, and the second
pass actually filled in the buckets.

As always, I'd be glad to help implement...

Charles