Fix pypi upload

• Drop support for Python 2
• Add django filters for markdown and html
• Tested against release version of Django 1.8
• Add THUMBNAIL_FORCE_FORMAT
• Add THUMBNAIL_FALLBACK_FORMAT
• Change THUMBNAIL_DUMMY_URL to use keyword arguments in string format

• Add support for base64 encoded images as source
• Add support for colormode through setting the option colormode or the setting
  THUMBNAIL_COLORMODE.

• PgmagickEngine
• WandEngine
• Higher maxblock in PillowEngine.engine_raw_data

• Add Django templatetag get_thumbnail
• Catch IOError and OSError in PillowEngine.engine_load_image and throw ThumbnailError, which
  will be caught in get_thumbnail if THUMBNAIL_DEBUG = False.

• Expendable image engine, storage backend and cache backend
• PillowBackend
• FilesystemStorageBackend
• SimpleCacheBackend
• RedisCacheBackend
• Django integrations
  • DjangoStorageBackend
  • DjangoCacheBackend
  • Settings integration and defaults for django
• Support for dummy thumbnails