edit README and remove py-gobject in favour of py-gobject3

Dockerfile

@@ -26,7 +26,6 @@ RUN \
 	libpng \
 	nano \
 	openjpeg \
-	py-gobject \
 	py-gobject3 \
 	py-pip \
 	python \

README.md

@@ -64,6 +64,8 @@ Edit the config file in /config
 
 To edit the config from within the container use `beet config -e`
 
+For a command prompt as user abc `docker exec -it -u abc beets bash`
+
 See [Beets][beetsurl] for more info.
 
 Contains [beets-copyartifacts](https://github.com/sbarakat/beets-copyartifacts) plugin, [configuration details](https://github.com/sbarakat/beets-copyartifacts#configuration)