fix: try to speed-up build

Author: bednar

tox.ini

@@ -14,10 +14,10 @@ deps = -r{toxinidir}/requirements.txt
        py36: numpy==1.15.4
        py37: pandas==0.24.2
        py37: numpy==1.16.2
-       py38: pandas==0.24.2
-       py38: numpy==1.17.2
-       py39: pandas==0.24.2
-       py39: numpy==1.16.2
+       py38: pandas==1.1.2
+       py38: numpy==1.19.0
+       py39: pandas==1.1.2
+       py39: numpy==1.19.0
 # Only install pandas with non-pypy interpreters
 # Testing all combinations would be too expensive
 commands = nosetests -v --with-doctest {posargs}