BUG FIX: Fix for Chrome Mobile

On Chrome Mobile (Nexus 7), images are not visible (just a dark
background). The fix was to set visibility:hidden on the ul element
containing the slides and to make sure the first slide was set to
visibility:visible. This is a bit counter-intuitive and I can't explain
why it works, but it does without having any apparent negative
consequences on other browsers.
Hide progress bar & move slide bullets

When the title is long or a user's screen is small, the title and slide
bullet list can render on top of each other. To minimize this, I made
two changes (1) Right align the bullet list (2) Use a CSS media query to
show the list only for larger screens (> 800px wide). I also forced the
progress bar to be completely invisible when it is disabled
(progress_bar=0).