Docs: <appname> -> <AppName> to avoid confusion

See ActiveState/appdirs@d6e084c104c702aabcad1a914fb9ec64bf41b8fc

We were not messing with appname, actually, which is good,
only the docs was "incorrect".
Docs: comment on appauthor -> appname fallback

ActiveState/appdirs@0826614d35be125f4637d01a5b1c5b628cb43fc2
The fallback was already in place.
Only use version if appname is not NULL

ActiveState/appdirs@71d586aef3d82ba4752bbdc8d3f241a5b751f73c
warn when appname is null
Add test for warning when appname is null

* one test should be enough for this behaviour
(not sure I understand the whitespace formatting in this block)
Merge pull request #5 from jefferis/feature/gaborcsardi-sync-appdirs

Feature/gaborcsardi sync appdirs