Add number to container

fig/container.py

@@ -46,6 +46,13 @@ class Container(object):
     def name(self):
         return self.dictionary['Name'][1:]
 
+    @property
+    def number(self):
+        try:
+            return int(self.name.split('_')[-1])
+        except ValueError:
+            return None
+
     @property
     def human_readable_ports(self):
         self.inspect_if_not_inspected()