Allow skip on module level messages

[snudler6]

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[snudler6]

resolves #418

[bsamseth]

While this works for the test case, it doesn't work if there is a comment before the module docstring. An example that still reports and error:

# -*- coding: utf-8 -*-
# noqa: D400
"""No period at the end""" 

Encoding pragmas, or #!/path/to/python comments are quite common, so I think this should be fixed to account for this.

I've added a PR with a fix, see #446