Add section for extending

Update changelog & version bump

Bump to v1.0.0!

Ignore .virtualenv

Merge pull request the-paperless-project#247 from danielquinn/issue/235

Allow correspondents to be deleted without deleting their documents

Remove debugging info

Drop SHARED_SECRET in favour of EMAIL_SECRET

Originally we used SHARED secret both for email and for the API.  That
was a bad idea, and now that we're only using this value for one case,
I've renamed it to reflect its actual use.

Preparing for 0.5.0

I hadn't realised that I hadn't released 0.5.0 yet, so I've amended the version numbers

fix: allow for caps in file name suffixes the-paperless-project#206

@schinkelg ran aground of this one and I took the opportunity to add a
test to catch this sort of thing for next time.

Merge pull request the-paperless-project#203 from danielquinn/feature…

…/reminders

Feature: Reminders