Fixed #27 and #28:

* A history of 5 most recent local projects is now kept (local to the
  machine), this number is not yet configurable.
* If the Chrome app is not running when `zed` is run with a local server,
  it will now buffer up to 25 of these requests and open them all up when
  the Zed app starts (yay Go's channels which makes this very easy to implement).