Improve user+developer feedback when URLs are not mounted.

In the edit page, display a ImproperlyConfigured error when developers
neither included the urls.py nor django-fluent-pages "app node" integration.

In the list page, users could get an error when the "Blog page" node is
removed while there are still blog entries in the database.
Added missing south migrations for `blogpage` app.
Admin UI improvement: display latest blog entries in BlogPage plugin

This uses the template layout from the latest django-fluent-pages master;
to display a list of blog entries after the first fieldset.
Clarify base template usage, included instructions.

Previously too much automagic was happening, so a "base.html" would be
displayed without any blog contents. Now developers have to explicitly
define the base template, so this confusion no longer happens.
Simplify and document integrating comments

- Document the base template tags.
- Document how to use other commenting systems.
- Automatically include the django-fluent-comments CSS/JS files when available.
Rewrite/reorder README for readability
Make the default fluent_blogs/base.html less exclaiming
Fix unneeded double rendering of blog contents
Add BLOG_LAYOUT variable to reuse entry_archive/item.html easier
README: document template granularity
Fix author_name in author-archive template
Fix `fluent_blogs/base.html` example paths.
Fix import locations of `fluent_contents` classes
Add Django 1.5 user model support

Move Django compatibility features to `fluent_blogs.utils.compat`,
similar to django-fluent-pages
Ported template tags to django-tag-parser

Removed duplicate "tagparsing" library that also existed in other
django-fluent-* apps.
Added default/missing templates for {% get_entries %} and {% get_tags %}
Updated setup.py trove classifiers
Fix 500 error in sitemap when there are draft items.

The tags/categories/authors which only contain draft items are now hidden.
Remove ununsed import
Improve appearance of blogpage when there are no blog entries.