Kill tasks that aren't running after 60 seconds.

By default, tasks which don't enter TASK_RUNNING after 60s should be
killed.  This parameter can be changed via command line with the
`--task_launch_timeout` switch.
Fixed Marathon's task accounting.

We must guarantee that Marathon will never launch more than N instances
for a given app (where N is the number of instances requested).
Bump version.
More task accounting fixes.

 - Refactored internal task state
 - Added task lanch rate limiting
 - Ensure we rebalance tasks periodically
Added app search endpoint.

When polling the app list HTTP endpoint, you can now search the app list by
'id' or 'cmd' using the HTTP URL query format, like so:

  http://marathon-host:5500/v1/apps/search?id=some-app
Fixed web UI redirection by proxy.

Instead of redirecting web requests to the other master, we'll just
proxy everything.