add support for stop_signal to compose file

Signed-off-by: Jonathan Stewmon <jstewmon@rmn.com>

compose/container.py

@@ -107,6 +107,10 @@ class Container(object):
     def labels(self):
         return self.get('Config.Labels') or {}
 
+    @property
+    def stop_signal(self):
+        return self.get('Config.StopSignal')
+
     @property
     def log_config(self):
         return self.get('HostConfig.LogConfig') or None
@@ -132,6 +136,10 @@ class Container(object):
     def environment(self):
         return dict(var.split("=", 1) for var in self.get('Config.Env') or [])
 
+    @property
+    def exit_code(self):
+        return self.get('State.ExitCode')
+
     @property
     def is_running(self):
         return self.get('State.Running')