Sort directory via case insensitive match
Add support for m4v format
Appropriately reset now playing state
Request session immediately on page load
Add Up Next queueing functionality.

Allows adding files to an up next queue and channel. The interface
is very crude right now, this will be improved in subsequent releases as
channel functionality gets fleshed out.

Notes:
* Does not automatically play the next file in the queue yet.
* Does not allow viewing the existing queue
* Does not allow modifying and updating the queue

See #11