Needs docs.

[meshy]

Ought to mention:

• the Orderable model-base,
• the OrderableAdmin admin-class,
• the OrderableTabularInline admin-class,
• orderable is required in INSTALLED_APPS (for templates),
• the fact that jQuery and jQueryUI sortable are required. See jQuery UI not loaded in admin #1. OBSOLETE
• the issues with unique_together
• a link to the CHANGELOG.

[meshy]

Related to #7