Add a very simple candidate view page
Fix the LibDem Twitter usernames
Let email address settings be configured from general.yml
Reorder keys in human-ppc-decisions.json to be alphabetical
Add a manual decision about a new PPC non-match
Smoother Facebook login

This asks for an email address from facebook and doesn't ask for a
username.  This means that the facebook log in works with a single
click on the facebook auth page.
Use appropriate fields for email / URLs for proper validation
Make sure Twitter username entries are properly cleaned and validated

This is the rest of the fix for #26
Redirect to the person view page after editing / creating a person

Fixes #31
When doing a deep-compare of arguments, don't turn None into repr(None)
Remove a now unused parameter
Remove an unnecessary (and broken) optional parameter

We shouldn't under any circumstances be generating IDs for people that
are just slugified names any more; they should be integer IDs based on
the maximum previous person ID - it's picked in
create_person_with_id_retries now.
Add tests for the current behaviour of get_person_data_from_dict
Allow fields to be cleared by setting them to empty

This is another effect of PopIt's non-standard behaviour in response
to PUT requests at the moment. (See
https://github.com/mysociety/popit-api/issues/95 )

We can fix this by making sure that simple fields are set to null if
they're not specified, and clearing links and contact details by setting
them to [] in the "purging" PUT before the real one.  sigh.

Fixes #33
Rename the create person URL, and use a separate template for it

This fixes an error where the wrong URL was posted to if you got to the
"add new person" form after a something on the new person form on the
front page failed validation (issue #32).