- Redirect for /docs/editor/troubleshoot.html
- Spec URL tweak (in nav menu)
- Mac continuous build -> 64 bit

Staged at:
http://buglets.dart-lang.appspot.com/docs/editor/troubleshoot.html
http://buglets.dart-lang.appspot.com/tools/editor/#download

Review URL: https://chromiumcodereview.appspot.com/15366005