Added ThrottleImageMap.

This throttled the number of concurrent images being loaded per map.  It makes it much more fair between the two maps instead of having a global queue where the first map (left) wins.
Implement oversampling in fractal generator.
Change the JSON returned by server to have extra nesting.

This allows more information beyond simply instance status to be returned to the web page.
Put some design notes into DESIGN.md.
Add some TODOs.
Continuous health checking and server stats.

* Implemented continuous health checking.  Will continually poll for server information.
* Go server exports stats now including tile render count and time.
* AppEngine server aggregates counts and produces a synthetic avg render time metric.
* New display widget for showing stat.
Start up only when all VMs are ready.

Also updated the TODO.
Fix throttled image map to abandon unloaded images when they aren't needed.
Add new button to reset stats on demand.

This is implemented as a call from the javascript to the individual servers.  Kind of hacky but easier than plumbing a new POST through the GAE app.
Switch to fluid grid system.

This allows us to take up more horizontal space for wide screen displays.
Rearrange layout of fractal demo.
Support jumpting to random POIs.
Fix size of spinner.
Throttled image map now tracks divs by ID instead of URL.
Make user data decorator thread safe and resistant to information leakage.
Update README to reflect changes in fractal demo.
Load discovery document from file instead of server.  Faster, cheaper and more reliable.
Switch to final Go 1.1 release for fractal demo.
Support load balancing!

Right now it only works for a single hard coded project but it is a
start.  Once the LB API is settled I can update this app to create the LB directly..
Only start showing map when we know the LB is forwarding requests.

Also plumbed in uptime metric and aggregated it.  This was a false start to solving LB timing problems but is useful code regardless.