Add test in polynomials.py
Add getitem in polynomials.
Polynomials test passes.
Add failing test for negative coefficients
Add sign, pass test.
Pass in var to parse_polynomial_string and make test pass.
Refactor signs.
Add exception, and test.
Get rid of 1 as coefficient
Add equality and tests.
Add failing test for parser
Refactor a little and add coefficients.
Do things more pythonically.