Honor .HA_VERSION in Makefile

Makefile

@@ -1,5 +1,6 @@
 IMAGE = homeassistant/home-assistant
 CONTAINER = home-assistant
+HA_VERSION = $(shell cat .HA_VERSION)
 HASS_BIN = python -m homeassistant
 VOLUMES = $(PWD):/config /etc/localtime:/etc/localtime:ro
 HASS = docker run -it --rm \
@@ -23,6 +24,6 @@ stop:
 destroy:
 	docker rm -f $(CONTAINER)
 pull:
-	docker pull $(IMAGE)
+	docker pull $(IMAGE):$(HA_VERSION)
 deploy: test destroy run
 upgrade: pull deploy