Remove $.browser calls, as jQuery 1.9 removes them

Unfortunately we still need to do UA sniffing to make things work, so we're rolling our own.
Allow palette option to be dynamically updated

Fixes #6
Allow all options* to be dynamically set after a widget has been created.

This now conforms to the usual way of doing things in a jQuery UI widget.
* except for the `hide` option, which is only an init option.
Add a direct `color` get/set method

Move the internal Color.js instance to the _color property to avoid namespace collision with the new method
Add slight padding between picker and preceding input