Use quantum core for update scheduling

Rather than requiring a traditional crontab install, the app now
leverages quantum-core (link below) to schedule the instance update/sync
task every 5 minutes. Some updates as a result:

  - The new job is scheduled at runtime in server.ex.
  - The update.exs script was refactored to be compiled along with the
    rest of the app as instances.ex.
  - Scheduler and Server modules were added for creating and executing
    the new update task
  - All shell scripts were removed, as they are no longer needed

https://github.com/quantum-elixir/quantum-core

mix.exs

@@ -27,6 +27,7 @@ defmodule Farside.MixProject do
       {:plug_attack, "~> 0.4.2"},
       {:plug_cowboy, "~> 2.0"},
       {:poison, "~> 5.0"},
+      {:quantum, "~> 3.0"},
       {:redix, "~> 1.1"}
     ]
   end