Publ v0.7.3

Publ v0.7.3 is now out, with the following changes:

• Properly handles markdown and HTML stripping in summary text
• Improves first-paragraph extraction for OpenGraph cards
• Reduces unnecessary image renditions for OpenGraph cards
• Finally deprecates the AUTHL_FORCE_SSL configuration setting
• Adds group display to the user information on the admin panel
• Fix the PyPI listing
• Make the image rendition cache purge mechanism actually, you know, work

Note that entry.summary now takes an optional parameter, markup, which defaults to True, for the sake of consistency with the rest of the Publ templating API. If you are using entry.summary to provide descriptive text for things (e.g. <a title="{{entry.summary}}"> or <meta name="description" content="{{entry.summary}}">) this will have to change to {{entry.summary(markup=False)}}.