Fix signup form cleaning when not using activation

Checking whether a username / email address is in use by an active
or unconfirmed account (for purposes of showing a helpful error
message) should take into account the value of
USERENA_ACTIVATION_REQUIRED: if this is False then any conflicting
attempt will incorrectly receive the 'This username is already taken...'
message as there will not be any associated UserenaSignup objects.
Bump version
Merge branch 'master' into exonian-master

Conflicts:
	userena/forms.py
Merge branch 'master' of github.com:bread-and-pepper/django-userena