Attempt to fix broken submenus on smartphones

This is apparently a known issue in Bootstrap 2.3.x, with a few proposed
solutions. This is the simplest:
https://github.com/twbs/bootstrap/issues/7968
Add diagnostic border for mobile testing
Forcing CSS for mobile submenus (test)
Remove test code, add comment for submenu fix
Merge pull request #329 from OpenTreeOfLife/mobile-submenu-fix

Fixes broken submenus on Android, waiting for iOS results...