Documents $.fn.dragonSlider and related APIs.

README cleanup.

Fixes some API inconsistencies in $.fn.dragonSlider and makes it more
consistent with other jQuery APIs.

Squashed commit of the following:

commit dcf63dacd37d709e8cae28571de7f696ce0763b0
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 20 22:58:50 2013 -0700

    README cleanup.

commit 320291f861bdf165937c258b7f9e09a168b9790a
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 20 22:52:17 2013 -0700

    Fixes snap-to-click bug.

commit 2e70f9cc7ec2c98a29a50a7c829e5b700416054b
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 20 22:47:23 2013 -0700

    README cleanup and linting.

commit 46cec394b32b3fb06141a9c50319a8ee27a7c7ff
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 20 22:29:23 2013 -0700

    Fixes returns and adds slider docs.

commit 661eadeae035d9d0c6fe170e6a69af36dc666592
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 20 21:57:53 2013 -0700

    Adds .jshintrc and does some slider cleanup.