Update python requirements

Generated using pipenv:

  $ pipenv lock -r > requirements.txt
  $ pipenv lock -r -d > requirements-dev.txt

requirements-dev.txt

@@ -5,10 +5,10 @@ backcall==0.1.0
 decorator==4.4.0
 entrypoints==0.3
 flake8==3.7.8
-importlib-metadata==0.19
+importlib-metadata==0.19 ; python_version < '3.8'
 ipython-genutils==0.2.0
 ipython==7.7.0
-jedi==0.14.1
+jedi==0.15.1
 mccabe==0.6.1
 more-itertools==7.2.0
 packaging==19.1
@@ -24,9 +24,9 @@ pyflakes==2.1.1
 pygments==2.4.2
 pyparsing==2.4.2
 pytest-clarity==0.2.0a1
-pytest==5.0.1
+pytest==5.1.1
 six==1.12.0
 termcolor==1.1.0
 traitlets==4.3.2
 wcwidth==0.1.7
-zipp==0.5.2
+zipp==0.6.0

requirements.txt

@@ -3,13 +3,13 @@
 certifi==2019.6.16
 chardet==3.0.4
 idna==2.8
-numpy==1.17.0
-pandas==0.25.0
-pycountry==19.7.15
+numpy==1.17.1
+pandas==0.25.1
+pycountry==19.8.18
 python-dateutil==2.8.0
 python-stdnum==1.11
 pytz==2019.2
-requests-cache==0.5.0
+requests-cache==0.5.2
 requests==2.22.0
 six==1.12.0
 urllib3==1.25.3