Scheduled weekly dependency update for week 21 (#181)

* Update babel from 2.6.0 to 2.7.0

* Update pygments from 2.4.0 to 2.4.1

* Update requests from 2.21.0 to 2.22.0

* Update sphinx-intl from 0.9.12 to 1.0.0

* Update sphinxcontrib-websupport from 1.1.0 to 1.1.2

* Update tox from 3.10.0 to 3.12.1

* Update tqdm from 4.31.1 to 4.32.1

* Update urllib3 from 1.25.2 to 1.25.3

* Update virtualenv from 16.5.0 to 16.6.0

requirements/constraints.txt

@@ -2,7 +2,7 @@ alabaster==0.7.12
 appnope==0.1.0
 atomicwrites==1.3.0
 attrs==19.1.0
-Babel==2.6.0
+Babel==2.7.0
 backcall==0.1.0
 certifi==2019.3.9
 chardet==3.0.4
@@ -38,28 +38,28 @@ ptyprocess==0.6.0
 py==1.8.0
 pycodestyle==2.5.0
 pyflakes==2.1.1
-Pygments==2.4.0
+Pygments==2.4.1
 pyparsing==2.4.0
 pytest==4.5.0
 python-dateutil==2.8.0
 pytz==2019.1
-requests==2.21.0
+requests==2.22.0
 requests-toolbelt==0.9.1
 simplegeneric==0.8.1
 six==1.12.0
 snowballstemmer==1.2.1
 solar-theme==1.3.3
 Sphinx==2.0.1
-sphinx-intl==0.9.12
-sphinxcontrib-websupport==1.1.0
+sphinx-intl==1.0.0
+sphinxcontrib-websupport==1.1.2
 toml==0.10.0
-tox==3.10.0
-tqdm==4.31.1
+tox==3.12.1
+tqdm==4.32.1
 traitlets==4.3.2
 twine==1.13.0
 typed-ast==1.3.5
-urllib3==1.25.2
-virtualenv==16.5.0
+urllib3==1.25.3
+virtualenv==16.6.0
 wcwidth==0.1.7
 wsgi-lineprof==0.7.0
 wsgi-static-middleware==0.1.2