Added gitlab-ci.yml for automated testing & fixed environment-cpu.yml

1 job for gitlab-ci in 4 minutes and 25 seconds (queued for 47 seconds)
Name Stage Failure
test Test
    run(args, parser)
File "./", line 69, in run
with open(args.config_file) as f:
FileNotFoundError: [Errno 2] No such file or directory: 'experiments/tests/global_obs.yaml'

real 0m4.274s
user 0m3.523s
sys 0m0.682s
ERROR: Job failed: command terminated with exit code 1