Instead of failing when there is an unknown Akoma Ntoso element, log an error
Python 3 decode() fixes.

Need to decode() before running regular expressions, importing JSON, and
to do a str 'in' check ("Type str doesn't support the buffer API").
Remove caching from example project.
Remove direct django-tastypie dependency.

Use different working versions, for different versions of Django and
Python.
Allow code to run if tastypie is not installed.
Merge remote-tracking branch 'james/an'
Add option to skip files we already have.

Passing --skip-existing to the scraper will mean it does nothing
with files which we have already successfully downloaded and converted
to text.