cleanup continuous integration

requirements_continuous_integration.txt

+# contains all additional requirements to run the ```tox .``` in addition to requirements_dev.txt for ```tox -e py37,py37```
 bumpversion==0.5.3
 wheel==0.32.1
 watchdog==0.9.0

requirements_dev.txt

-# contains
+# contains all requirements to run the tests by running ```tox -e py36,py37```
 tox==3.5.2
 twine==1.12.1
 pytest==3.8.2

tox.ini

@@ -56,6 +56,9 @@ passenv =
     HTTP_PROXY
     HTTPS_PROXY
 whitelist_externals = sh
+deps =
+    -r{toxinidir}/requirements_dev.txt
+    -r{toxinidir}/requirements_continuous_integration.txt
 commands =
     sh -c 'ls benchmarks/*.py  | xargs -n 1 python'
 
@@ -71,9 +74,6 @@ passenv =
     HTTPS_PROXY
 deps =
     -r{toxinidir}/requirements_dev.txt
-; If you want to make tox run the tests with the same versions, create a
-; requirements.txt with the pinned versions and uncomment the following line:
-;     -r{toxinidir}/requirements.txt
 commands =
     sh -c 'echo DISPLAY: $DISPLAY'
     py.test --basetemp={envtmpdir}