Remove multi_part plugin

As part of our continuing effort to move plugins their own repository,
this plugin was moved to the pelican-plugins repository.
Nuked spurious ./tests directory

Only images, someone added a bit too much to the index
Fix for issue #219: tags should list only main articles, not translations
Fix webassets tests when running on a system with a different locale.
Merge pull request #810 from avaris/translations_in_tags

Fix for issue #219: tags should list only main articles, not translations
Merge pull request #809 from cdunklau/clean_up_images

Nuked spurious ./tests directory
fixed related_posts plugin
Merge pull request #813 from avaris/fix_related_posts

fixed related_posts plugin
Fix for issue #392
Merge pull request #819 from avaris/test-warning

Fixes issue #392
Merge pull request #807 from saimn/fix_webassets_tests

Fix webassets tests when running on a system with a different locale.
Added WordPress content decoding to importer