I often found myself writing code like if a.extension == 'png' and
trying to remember if I'm supposed to compare against 'png' or '.png',
and then it would trip up on files like A.PNG because I forgot to
lower() it.
So this class handles all that for you. You can == against it and it
will use os.path.normcase to give you OS-appropriate case sens,
and == works whether you include the dot or not. Then you can use
ext.with_dot or ext.no_dot to get reliably dotted strings.
I am considering some other instance attributes similar to force_sep.
And since these need to be carried over into newly spawned Paths,
I want to consolidate that into a single method so I don't have
to risk forgetting it on a new object.
The literal function will still be a bit more strict on the types
it accepts, but if you have something that you know is okay
to iterate you can call listify directly.
