lots of changes re: prep for mobile

 * debug route is gone, and index route simplified
   * no longer a need to store all pantries at bottom of page
 * HTTP 400 rather than 500 on geocoding fail
 * #content div is gone; wasn't necessary
 * rename of key div's:
   * #mainHeader -> #header
   * #leftContainer broken up; won't really be 'left' for mobile
     * #search followed by #pantryList
 * #searchIndicatorBar is gone
   * messages not super helpful + space is important for mobile
   * search() function replaced by underlying Backbone fn
 * #pantryList scrolled to the top on getting new results
   * first result always the closest one to the center of the map
 * #social moved towards the bottom, which will help page load perf
 * minor CSS tweaks