Move awkwardly placed paragraph.

[skip ci]
Require argvard >= 0.3.0
Move radicale back into main repo
Add missing word

[ci skip]
Add CONTRIBUTING.rst
Goddamnit rst.
Fix tests
Fix more tests
Fix even more tests!

lol rfc inconsistency
Make CaldavStorage.list faster

This will break all tests, see
https://github.com/Kozea/Radicale/pull/144