Ignore cpp/contrib and js/contrib

Fixes "dirty"-ness from clone location of:

mediawiki/extensions/Parsoid/cpp/contrib/libhubbub
mediawiki/extensions/Parsoid/cpp/contrib/pugixml
mediawiki/extensions/Parsoid/js/contrib

gwicke: rebased on master

Change-Id: I0b77d9cf282446c531f953d63ee23e14a7cc3cb8
Merge "Ignore cpp/contrib and js/contrib"