Support validating Django templates by compiling them

[rpatterson]

This automatically assembles test cases for every template under a template directory and compiles it. I used this for a large refactoring to find a few path updates I missed but I imagine it would be handy for other things too.

I'm happy to add tests for this if you can help me figure out how to do that. :-)

If you don't want to merge this, please let me know so I can break it out into it's own package. Thanks!

[rpatterson]

Any word on this? I'm happy to merge and release myself if you want? Or should I move this to a separate add-on?

[jwhitlock]

This is interesting, but there's too many existing broken feature to take on new ones. I think it would make a good stand-alone plugin, and we could add a link to the docs. And maybe use it as an example for spinning out some of the broken features into their own plugins...