Bugfix: key needs to be removed from list not popped.
Bugfix: remove instead of pop in insert.
Bugfix: __setitem__ is used for updates as well, if a key exists prior it should not be updated unless explicitly calling insert.
Merge branch 'master' of https://github.com/JustusW/BetterOrderedDict into JustusW-master

Resolved a conflict related to my adding docstrings.

Conflicts:
	better_od/core.py