TODO

TODO:

Computation:
Optimise (better bounds, etc).
Speed up companion matrix calculation (esp. spurious calculations of companion').
Improve routines in Polynomials module, especially memory consumption.

Colouring:
Allow output of transparent png files.
Change strings to Word8, Word24 etc in hex parsing.
Clean up source colouring: polynomial coefficients should have abstract labels,
    preventing any kind of coefficient matching issues...

Gradients:
Clean up gradient specifications, and allow parsing of transforms.

Comments:
Add comments everywhere, with documentation.

Roots:
Add scale factor utility in some form.

General:
Command line parameter to determine output file.
Flip y-axis in image routines.
Cleanup using roots/ifs, source/density, different coeffs... uniformly!
As per http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/sooner-faster-quicker.html
    remove unnecessary instance derivations.