Make sure 'twisted' doesn't appear in the egg-info top_level.txt file.
Wokkel provides a plugin for twistd. As with all twisted plugins, these need to be placed in a directory twisted/plugins so that the plugin mechanism can find them. This is not a real package, and when building eggs the directory must appear in the egg. However, 'twisted' should not occur in the top_level.txt file as this causes warnings when importing twisted, and triggers a bug in pip that removes all of twisted when a package with a twisted plugin is removed.
This change overrides the way the top_level.txt file is written, by explicitly excluding 'twisted'.