Add tests and refactor polynomial.py

[smkuls]

• Refactoring and cleaning up polynomial.py
• Adding tests to verify the functionality of the methods

[codecov-io]

Codecov Report

Merging #51 into dev will increase coverage by 2.30657%.
The diff coverage is 100%.

@@                 Coverage Diff                 @@
##                 dev         #51         +/-   ##
===================================================
+ Coverage   74.08231%   76.38889%   +2.30657%     
===================================================
  Files             11          11                 
  Lines            899         864         -35     
  Branches         150         142          -8     
===================================================
- Hits             666         660          -6     
+ Misses           206         183         -23     
+ Partials          27          21          -6

[sbellem]

We can make use of the following fixtures: https://github.com/initc3/HoneyBadgerMPC/blob/dev/tests/conftest.py#L27-L38

[sbellem]

p.s.: If using the fixtures, you'll need to invoke them for each test function: e.g.:

def test_poly_eval_at_k(GaloisField, Polynomial):
    poly1 = Polynomial([0, 1])  # y = x
    # ...
    coeffs = [randint(0, GaloisField.modulus-1) for i in range(d)]
    # ...