Suppress autodoc on __main__

The pull request includes a very modest whitespace change and an update to exclude modules named '__main__'. A module __main__ is used, particularly in Python 3, to provide an entry point for a package. Where one might execute a package using "python -m my.package", the implementation might reside in my.package.__main__.  __main__ modules are typically executed and not imported. Therefore, they should not be included in autodoc sources.