Remove dead assignment.

It was just there for consistency, but the analyzer is happier this way.
Don't leak CFStringRefs when formatting date/time.

Found by the Clang analyzer.
Use CFURLCopyResourcePropertiesForKeys to display dates.

Remove backup date as I can't find a high-level, non-deprecated way to retrieve it any more.
Spacing fixes.
Mark kCFURLFileResourceTypeKey as used.
Update README.
Potentially fix crash in CFURLGetFSRef introduced in 9a595f1a.

CFURLCopyResourcePropertiesForKeys may have been using, but not retaining, the keys array?
Add __attribute__((__noreturn__)) to functions that don't return.

Makes the analyzer happier, since it doesn't seem to know that exit() won't return.
Work around OS X bug causing overrelease of CFURL string.
Revert change in 8f9f31b1; it didn't do anything.