0.3.0: Support async auth, cleanup

This is version 0.3.0.

- Support asynchronous authentication function (thanks mmalecki).
  This closes #6.
- Remove some cruft from the tree.
- Call the returned function "middleware" per convention.

Squashed commit of the following:

commit 9fca8aa73270c165bf2d0c8f8c173594d049bde2
Author: Tony Gies <tgies@tgies.net>
Date:   Mon Mar 17 10:23:41 2014 -0500

    0.3.0

commit 068bd7cb21878a5d2480250e8fb34d2f737c8800
Author: Tony Gies <tgies@tgies.net>
Date:   Mon Mar 17 10:21:25 2014 -0500

    Don't track .gitignore

commit 15a72e40f0570ac2f4ea993fdcd2c033699177c9
Merge: 4759317 cb6be60
Author: Tony Gies <tgies@tgies.net>
Date:   Mon Mar 17 10:18:47 2014 -0500

    Merge remote-tracking branch 'mmalecki/async-authorization' into develop

commit cb6be60d921facaf751ab8203478b12dc4c65133
Author: Maciej Małecki <me@mmalecki.com>
Date:   Mon Mar 17 15:20:13 2014 +0100

    Allow asynchronous authorization

commit 4759317c0b681d8203907366f4f592395be7eb1f
Author: Tony Gies <tgies@tgies.net>
Date:   Wed May 8 08:27:54 2013 -0500

    Name the returned function "middleware"