Added new event handlers

Added onBeforeOpen, onBeforeClose, onBeforeSlide, and a new onSlide handler to match the existing onOpen and onClose.

Documentation about scrolling panels

Updated readme.md to explain how to achieve panels with scrolling content, and link to new JSFiddle which demonstrates it.

Introduce click filtering

A few improvements, mainly more control over which clicks outside the tabs will close them. Also documentation and demo improvements.

Fix panel positioning when content changes size

Now gracefully handles tab positioning when panel content changes size, see #8.

(Slide in and out are now CSS animations.)

Fix

Fix for #5.

Auto-detect tabImage size if possible, and don't rotate image

If a tab image is used, it is no longer rotated, and the width/height is autodetected (works on IE9+, otherwise supply the width and height at init time).

Default to 'fixed' positioning.

Tabs now stick to the window edges rather than scroll with the content, by default.

v2.2

Significant revision of library and documentation, including JSFiddle demo.