A couple of tools tack on column information and error codes in their

own way, without there being any consistency between the approaches.

Most completely throw out this information.
This attempts to add some consistency by adding error_code and

start_column parameters to File.comment(). This will modify the

text, appending column and error code information.
While in there, I've fixed up the flow of logic to avoid setting or

computing state that won't be used (for instance, line information when

we know we won't be commenting on any lines).
Unit tests were added for all file commenting conditions.

Unit tests pass on Python 2.7 and 3.x.