chapter-03/recipe-03 Docker image does not include numpy library

Hi, this is just a minor issue I found on the docker image https://hub.docker.com/r/devcafe/cmake-cookbook_circleci_ubuntu18.04.

On chapter-03/recipe-03, the numpy library is required but not installed on the conda directory.
 
I just fixed it installing it with pip, but I thought I let you know, thanks.