This is the Heatbug demo app.  The code is very well commented,
so the only thing that needs to be said here is that if you want
to see little pictures (pixmap) running around instead of squares,
then simply replace the normal .h and .m files with their 
corresponding .h.pixmap and .m.pixmap, respectively and 
recompile.  Note that only Heatbug.h, Heatbug.m, HeatbugModelSwarm.h,
and HeatbugModelSwarm.m need to be replaced.


