html cleanup

 * removed some old commented code
 * reformat
 * removed one excess div
Removed old footer CSS
cleanup
[css] save space on small screens
Provide responsive layouts
switched from black to white header

 * looks cleaner and border looks better now
fix: respond on window, not device, width
removed commented / unused code
tighten spacing on small screens
Initial history api support

* Update browser history on photo load
* Returning to an item via browser history should work
properly handle height, including border

* previously, #map top border didn't appear
keep width to 100%
History api and page loading improvements

* On page load, check if photo/story id is supplied and load if so
* On popstate event, ensure state exists before using it
Parse height as float, not int, to avoid rounding error
cleanup, standardized margin/padding for <p>
When clicking header, prevent page reload
On desktop layout, fade out text on screen bottom; visual clue for scrolling
Remove excess </div> tag
On mobile layout, move photo above text
Put letter scrollbar on the left side of content. 

* This allows the photo caption and letter content area to appear more
   connected (without a scroll bar separating the two areas), and looks 
   better since the caption is flush left.