rethink bookmarkable URLs for all states of the site

[simgan]

in addition to permalinks for event detail window, user should ideally be able to get a bookmarkable permalink that captures the state for:

• the map: long, lat, zoom level
• the event popup window: which one is open, if any
• and of course, the state of the timeline, which we already have

once we implement issue #15, the permalinks that that allows the user to save should be whatever system we design and implement for this issue.

this is also related to issue #80 (not always necessarily appending the timeline min/max)