Add an uptime endpoint for Pingdom.

Sends a simple database query to see if we can still connect
to the database. Should help us detect issues like yesterday's
EC2 issues earlier.

lib/travis/api/app/endpoint/uptime.rb

@@ -0,0 +1,16 @@
+require 'travis/api/app'
+
+class Travis::Api::App
+  class Endpoint
+    class Uptime < Endpoint
+      get '/' do
+        begin
+          ActiveRecord::Base.connection.execute('select 1')
+          [200, "OK"]
+        rescue => e
+          [500, "Error: #{e.message}"]
+        end
+      end
+    end
+  end
+end