A set of walk-throughs to gradually learn how to use PETSc via the petsc4py package.

1. vec_serial.py - work with vectors on a single process.
2. mat_serial.py - work with matrices on a single process.
3. ksp_serial.py - solve a linear system on a single process.
4. da_serial.py - work with distributed arrays on a single process.
5. da_maxwell_serial.py - solving maxwell's equations.

1. Implement a 2D E&M solver (that will work well with both modes).

1. Remove "long way" comments in serial codes.
2. Do something with the maxwell 3D code.