bump test requirements

also ignore celery improvements

requirements_for_test.txt

@@ -1,11 +1,11 @@
 -r requirements.txt
 pycodestyle==2.3.1
-pytest==3.0.1
-pytest-mock==1.2
-pytest-cov==2.3.1
+pytest==3.1.3
+pytest-mock==1.6.2
+pytest-cov==2.5.1
 coveralls==1.1
-moto==0.4.25
-flex==5.8.0
-freezegun==0.3.7
-requests-mock==1.0.0
+moto==1.0.1
+flex==6.11.0
+freezegun==0.3.9
+requests-mock==1.3.0
 strict-rfc3339==0.7