Update the docker image to a custom test suite

.gitlab-ci.yml

@@ -32,17 +32,10 @@ python-2:
 # test example on python 3
 python-3:
   stage: test
-  image: continuumio/anaconda3
+  image: gregoryashton/bilby-test-suite-py3
   before_script:
-    - apt-get update
-    - apt-get install gcc -y
-    - apt install -y libgl1-mesa-glx
     - pip install -r requirements.txt
     - pip install -r optional_requirements.txt
-    - pip install 'coverage>=4.5'
-    - pip install coverage-badge
-    - pip install flake8
-    - pip install pytest-cov
   script:
     - python setup.py install