Changed $ to jQuery for interop

I suggest this change ("jQuery" instead of "$" in JavaScript code) because the two are interchangable, but the "$" shortcut is used by several JavaScript libraries (most notably Prototype). If the developer maintains older code that includes the Prototype library and adds jQuery for new code, a conflict occurs. Also, ones code might get included in pages that reference other JavaScript libraries, equally resulting in a conflict. These conflicts are hard to debug and thus I'd consider it best practice to use jQuery instead of $.