move unit test files into module

[lundybernard]

change absolute to relative imports

[lundybernard]

> pytest
======================================= test session starts ========================================
platform linux -- Python 3.9.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: ~/projects/Knots
collected 58 items                                                                                 

braidgenerator/tests/braidword_test.py ........................................              [ 68%]
braidgenerator/tests/markovchain_test.py ..................                                  [100%]

======================================== 58 passed in 0.36s ========================================