makeCollapsible fix for jQuery 1.6.1

makeCollapsible fix for jQuery 1.6.1
* Pre 1.6, jQuery returned an empty string for attributes that were not set. Although in a way that was wrong, it was the way it was. From jQuery documentation: "As of jQuery 1.6, the .attr() method returns <code>undefined</code> for attributes that have not been set." [1]
** Fixing makeCollapsible by removing empty-string checks and casting to boolean instead
* Wrapped a long line

[1] http://api.jquery.com/attr/

(jQuery 1.6.1 upgrade was in r89866)