coded.  I also increased the default threshold to a more reasonable value.  The previous
value hardly excluded any points and gave a slightly worse average precision on a standard
test dataset.

based on the input pixel type rather than always using long.

on C++11 compilers.

iostream::tie() to implement its "auto flush on read" feature to use the sockstreambuf's
own auto flushing mode instead.

buffers before performing any network reads.

is so they are safer to use in threaded programs.

I also changed it's interface slightly.  In particular, I removed the min_diff
parameter and replaced it with an explicit min_size parameter.

parallel_for routines.

verbose time remaining estimation.