visually distinguished totally metal-depleted rubble
added note to restore conservation of mass later
made conveyor desc more correct from user perspective
Started brewing up some gas physics code.
Hacked at the gas physics some more.
Merge branch 'master' of https://github.com/idupree/Lasercake
crudely, let you watch tetrahedrons move
Made things a reasonable scale (m, not nm, in size).
Switched to nonconvex/holey polyhedral regions
adjusted some locations and sizes
Switched to a plane-centric model.

We no longer define vertices except as a function of
   the locations of their incident planes.
Fixed bug where velocity didn't update
fixed name of misleadingly-named function
implemented "when planes collide" function

(didn't test)
fixed using wrong type
initial mostly-untested fixed-size-bignum implementation
add compile-tests for bignum
Merge branch 'master' of https://github.com/elidupree/Lasercake
bignum: add some tests, fix some bugs