space_robots README indicates wrong path when calling source

[ivanperez-keera]

When I connect to a running docker container as indicated in:

docker/space_robots/README.md

Lines 48 to 52 in 76cd412

	Open a new terminal and attach to the currently running container:
	```
	$ docker exec -it <container-name> bash
	```

I am root in the container, not running as the spaceros user. That means that the lines:

docker/space_robots/README.md

Lines 54 to 62 in 76cd412

	Make sure packages are sourced:
	```
	$ source ~/spaceros/install/setup.bash
	```
	```
	$ source ~/demos_ws/install/setup.bash
	```

don't execute correctly because that path does not exist in the root's home directory.

Either something is wrong with the images, or they should just say:

$ source ~spaceros/spaceros/install/setup.bash 

$ source ~spaceros/demos_ws/install/setup.bash