Simplify fix_map

Part of #72
Simplify fix_filter

Part of #72
Simplify fix_zip

Part of #72
Simplify fix_print

Closes #66
Merge remote-tracking branch 'upstream/master' into simplification
Skip six imports for map and filter when changed to a list comp
Merge branch 'master' into simplification
Remove dead imports
Merge pull request #75 from brettcannon/simplification

Simplify various fixers