Test: rewrite xbrl.remove_namespace_date() test

Test should expects a new element to be returned.
Rewrite xbrl.remove_namespace_date()

Rewrite function to strip date from company namespace using lxml.
Rewrite bridge_prep() to use lxml

xbrl.remove_namespace_date() returns a new elem, bridge_prep() now
reflects that.
Copy attributes to new root in xbrl.add_namepsace
Version bump to 2.0.2