Adding `parent_id` parameter to `Discussion.posts` method
Merge branch 'develop' of https://github.com/ImaginationForPeople/assembl into develop

Conflicts:
	assembl/synthesis/models.py
Fleshed-out Extract model.
Merge branch 'develop' of https://github.com/ImaginationForPeople/assembl into develop
Merge branch 'develop' of https://github.com/ImaginationForPeople/assembl into develop
Extracts have a source, which is generic content. specify key for owner and creator. Alembic migration
saving the profile. Allow to change password, add extra email, etc.