Contrib/Markup documentation should mention requirement for external libraries

[hunajakippo]

​http://docs.djangoproject.com/en/dev/ref/contrib/#markup does not mention that libraries that do not ship with Django are required. This should be mentioned. Documentation refers to sources which indicate this.

I would suggest something like:

"To activate these filters, add 'django.contrib.markup'.." --> "To activate these filters, make sure required libraries are installed, add 'django.contrib.markup'.."

[steveed]

Added the required libraries.

[Gary Wilson]

(In [12860]) Fixed #13202 -- Documented required libraries for markup template tags, based on patch from steveed.

[Gary Wilson]

(In [12861]) [1.1.X] Fixed #13202 -- Documented required libraries for markup template tags, based on patch from steveed.

Backport of r12860 from trunk.

[Jacob]

Milestone 1.2 deleted