Use imagesLoaded plugin to detect image loading

Use the imagesLoaded jQuery plugin to detect when images are being
loaded to trigger our handler to resize the image containers and
captions.

Closes #622
Merge branch 'hotfix-622-scale_viewer_image_borders' into develop

Conflicts:
	README.rst
More robust search for django-admin.py

The apply_djang_patches script called from ci_before_script.sh started
failing in the Travis CI build.  The reason was that django-admin.py
wasn't being found.  Try executing the script directly, instead of being
called with ``bash`` from ci_before_script.sh and try explicitly activating
the virtualenv from ``apply_django_patches``.

Addresses #626
Log uncaught JavaScript errors to the server

Addresses #623
Merge branch 'hotfix-623-catch_js_errors' into develop

Conflicts:
	README.rst