* Added missing jQuery UI sprite files, causing collectstatic to throw errors (most reported on Heroku)
* Page system check for on_delete actions of ForeignKeys was throwing false positives when page class descends from an abstract class (Alejandro Giacometti)
* Page system check for on_delete actions of ForeignKeys now only raises warnings, not errors
* Elasticsearch configuration now supports specifying HTTP authentication parameters as part of the URL, and defaults to ports 80 (HTTP) and 443 (HTTPS) if port number not specified
* Fixed a TypeError when previewing pages that use RoutablePageMixin
* Rendering image with missing file in rich text no longer crashes the entire page
* IOErrors thrown by underlying image libraries that are not reporting a missing image file are no longer caught
* Fix: Minimum Pillow version bumped to 2.6.1 to work around a crash when using images with transparency
* Fix: Images with transparency are now handled better when being used in feature detection
In previous versions, an Elasticsearch connection URL in ``WAGTAILSEARCH_BACKENDS`` without an explicit port number (e.g. ``http://localhost/``) would be treated as port 9200 (the Elasticsearch default) whereas the correct behavior would be to use the default http/https port of 80/443. This behavior has now been fixed, so sites running Elasticsearch on port 9200 must now specify this explicitly - e.g. ``http://localhost:9200``. (Projects using the default settings, or the settings given in the Wagtail documentation, are unaffected.)