BaseReport Messages Include Error Row and Column Info

[astro-josh]

BaseReport (used when quiet option is specified) does not include row and column numbers or other useful error info. Being able to access this info even when quiet mode is enabled may be useful for some.

UseCase: User does not want the pep8 check error printed to stdout so they enable quiet mode. User may still want to retrieve errors from BaseReport messages within a python script that checks jupyter notebook code cells for pep8 errors and generate reports for CI.

Changes:

• Updated base report messages to a list instead of a dictionary. Stores tuples for error info.
• Updated methods to print and get statistics fro BaseReport to work with new messages format.
• Updated test_own_dog_food unit test to verify assertion on list of tuple instead of dictionary.