Portamento is a jQuery plugin that makes it simple to add sliding panel
functionality to your web page.
Include portamento.js in your page, just before </body>
wrapper - The sliding panel won't go out of its wrapper's boundaries, and
respects the wrapper's padding. (Default wrapper <body>)
gap - The number of pixels to leave between the top of the viewport and the
top of the sliding panel. (default value is 10 px)
disableWorkaround - Disable the workaround for not-quite capable browsers