Move definitions link and shade the text below.

Move the map legend definitions link below the map to
better differentiate it from other text at top, and
set a background on the call to action text below the
map, as suggested. (#577)
Change map legend definitions icon to a circled i.

Sid tested users with paper prototypes and found that
users did not recognize the question mark icon, but
did recognize an 'i' icon. Also changed the color
and capitalization of the Enlarge link below the
North America map to match a bit better. (#577)
Rebuild production JS file.