Support querying for dates other than today
Move the json fetching into a function
Add a header for the timeline with the date and navigation arrows
Query and display today's date on load

Add helper functions for turning JavaScript Date objects into strings
formatted for querying or for displaying.
Add behavior to change the date when clicking on the arrows
Add styles to the arrows

Don't ever underline these links, it looks weird. Turn the arrow gray
and turn off the hand cursor to make it look disabled when we want it
to.
Instead of inserting the gif, hide and show it and the map
Clear the timeline when we change dates
Move map initialization into a function we can recall

So that we can reset the map when we change dates.
Merge pull request #3 from carols10cents/previous_dates

Previous dates