Add health property to Containers model

Signed-off-by: Jay Turner <jay.turner@kayenta.io>

docker/models/containers.py

@@ -62,6 +62,13 @@ class Container(Model):
             return self.attrs['State']['Status']
         return self.attrs['State']
 
+    @property
+    def health(self):
+        """
+        The healthcheck status of the container. For example, ``healthy`, or ``unhealthy`.
+        """
+        return self.attrs.get('State', {}).get('Health', {}).get('Status', 'unknown')
+
     @property
     def ports(self):
         """