Refactor test_parquet.py to use check_round_trip at module level
Refactoring and unification of testing approach in `test_parquet.py` module. 

Iteration upon work that was done for https://github.com/pandas-dev/pandas/pull/19135#issuecomment-358161165

- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] tests added / passed
