requirements: update 'tox' (test)

Author: glarrain

requirements/test.txt

@@ -7,7 +7,7 @@ coverage==4.5.2
 flake8==3.7.6
 mypy==0.670
 #requests-mock==1.5.2
-tox==3.7.0
+tox==3.13.2
 
 # Packages dependencies:
 #   - codecov:
@@ -22,17 +22,25 @@ tox==3.7.0
 #       - typed-ast
 #   - tox:
 #       - filelock
+#       - importlib-metadata
+#           - zipp
+#       - packaging
+#           - pyparsing
 #       - pluggy
 #       - py
 #       - toml
 #       - virtualenv
-filelock==3.0.10
+filelock==3.0.12
+importlib-metadata==0.18
 mccabe==0.6.1
 mypy-extensions==0.4.1
-pluggy==0.9.0
+packaging==19.0
+pluggy==0.12.0
 py==1.8.0
 pycodestyle==2.5.0
 pyflakes==2.1.0
+pyparsing==2.4.0
 toml==0.10.0
 typed-ast==1.3.1
-virtualenv==16.4.3
+virtualenv==16.6.1
+zipp==0.5.2