Always return string from __str__.

If a Section lacked a heading, trying to print it out from the command
line would give a proxy error.
Require unicode-slugify for better slug i18n.

Along with an update to mysociety-django-sluggable, this means the
default slugify function for slug creation will be one that can e.g.
handle CJK names. Thanks to Mark Longair for investigating and tests.
Don't try and delete content type in migration.

There may be things still using the content type, for example admin log
entries, and it is better to leave those pointing at the content type
than remove them all as well.
Correct modified column name for Speaker.
Allow upscaling of thumbnails.
Bring back date on speech detail page.
fix display of speech types/dates on speech page
more translatable speech metadata
Merge branch 'issues/148-lost-speeches'
Merge branch 'issues/361-slugify'

Conflicts:
	setup.py
Fix speaker URL on speech detail page.
add new block to _home.html template
Merge remote-tracking branch 'origin/homepage-description-block'
Add an optional face cropping processor.

This can be used for small circular speaker images.
Show speech dates in all non-section speech views.

In a section it makes sense to not show a speech date if it matches
the date of the speech before, but when viewing a speaker or a set
of search results, the speeches are not an ordered group, so we should
show the date for every speech.
Unquote URL before saving image cache.

Also some Python 3 fixes, discovered by mocking less in order to test
more of the code flow.
Truncate image_cache filename for database field.