added scrollTo target functionality

I made it so that when you click next the page will scroll to 300
pixels above the target element. I didn't add the ability to have
settings, etc because I didn't need them, but I thought I would give
this extension back to the open source world anw.


Also, I don't know coffeescript so I made the changes in javascript first and then tried to add them to coffeescript. If there are syntax errors in the coffeescript please let me know. Thx.