Remove old_start, end_conversation and tag acquisition from conversation wrapper. Also fix all the things that relied on those.
pep8/pyflakes cleanup.
Merge branch 'develop' into feature/issue-639-old-conversation-cleanup-pt-1

Conflicts:
	go/contacts/views.py
Merge branch 'develop' into feature/issue-639-old-conversation-cleanup-pt-1
Merge branch 'develop' into feature/issue-639-old-conversation-cleanup-pt-1

Conflicts:
	go/conversation/views.py
Use helpers instead of status constants.
Merge branch 'develop' into feature/issue-639-old-conversation-cleanup-pt-1
Merge branch 'feature/issue-639-old-conversation-cleanup-pt-1' into develop