Require .path on IFilePaths and add it to MemoryPath.
Add some more information to docstrings.
memory: Fix parent() and sibling() to respect the root behavior.

Root's parent is also root, rather than bottom or an Exception.

Remove the custom sibling() as the version in AbstractFilePath is now suitably
correct for MemoryPath.

Also add a test case for all IFilePaths.
Remove get[acm]time() methods entirely.

> 2013
> Still using old methods deprecated half a decade ago
ISHYGDDT