v0.5.3: Merge pull request #15 from Wtower/devel

What's new

• Added feature: remove uploaded file (and any image styles-thumbnails) when the relevant record is removed.
• Improved documentation
• Improvements
• Upgraded to Django 1.9

All changes

• Fix #11
• Added help texts to models with reference to documentation
• Added images to the project
• Added more blocks in base.html.
• Fixes #8
• Added feature: remove uploaded file (and any image styles-thumbnails) when the relevant record is removed.
• Added pre-delete signal.
• It appears that multiple pre-delete functions with decorators do not get called, so merged function with
  previous delete_guardian_group_perms.
• Using added function in media.py to search for all files with the same name, below the path, in order to trace
  all thumbnails and then remove all.
• Updated tests to cover new feature.
• Minor update in readme.
• Modified code that returns the path of an uploaded media file be OS-agnostic
• Improved test to allow different title in admin (still containing "administration")
• Improved documentation
• Added class to index.html to improve navigation in inspector
• Added reference to django-ninecms-starter on readme
• Improved documentation

⚠️ Changes that require manual migration actions:

• Replace node.path with node.full_path when checking if active path in derived
  block_menu_header.html templates (Nov 29)