refactor site.js
Fix back button for scene 2 > scene 1. bug 824356

Add code so back button will take user to scene 1 from scene 2.
Adds '#download' hash to URL for modern browsers (IE9+).
Begin dl if arriving with #download in URL. Bug 824356

Two minor concerns:

- Possible race condition with pulling correct download link from
  DOM prior to window.load. Could duplicate DOM query in window.load
  to be safe.
- Install images may not be fully loaded if on slower connection. Not
  sure we can do much here.
Bug 824356: refactor new.js
Added missing alt-attribute on Firefox logo
Bug 764261: Redirect /zh-TW/* to mozilla.com.tw.
Bug 764261: Remove /zh-TW/ -> mozilla.com.tw until questions resolved.
Bug 828842 - broken link in /research/people
Bug 829091 - MWC 2013 Phase 1 landing page