Make background in dot transparent.
Fix up Makefile.
Fix in test setup and add in makefile rules.

Those makefile rules are almost sentient.
Add in minunit.h.
Add in check to ensure all elements are included.
Add in fitness check test.
Test asserting that red-black invariants work.
Test that nonuniform frequencies are correct.

(within some uncomputated confidence interval)
Testing uniform frequency.
Test duplicate allowance.
Test duplicate probabilities.
Continue running tests even if some fail.
Invert Makefile test responsibility.

Namely, enforce test Makefile to bring in dependencies from parent
directory, not vice versa.
Avoid printing a million lines when testing.