Avoid try: .. except ImportError: blocks about django-codemod

[browniebroke]

When I started this tool, I had in mind Django projects, not re-usable Django app. Django app usually need to target more than one version of Django, and will have these sort of imports.

This is indeed not supported yet, we should at least put up a warning or disclaimer somewhere until we handle it better.

I think it should be feasible by disabling the visitors temporarily using the context when inside of try/except blocks

[browniebroke]

I've added a paragraph in the readme to make this limitation clearer.