setup: Pin black to 19.10b0

The latest release of black wants to reformat all our code. We will from
now on be sticking with black version 19.10b0.

Fixes: #236

Signed-off-by: John Andersen <[email protected]>

Author: pdxjohnny

setup.py

@@ -57,7 +57,7 @@
             "sphinx",
             "sphinx_rtd_theme",
             "recommonmark",
-            "black",
+            "black==19.10b0",
             "jsbeautifier",
             "twine",
         ],