Add 3.8.1 as the upper max

Since we are currently not working on 3.8.2
#4

Author: gordonwatts

README.md

@@ -79,7 +79,8 @@ Comming:
 This code has been tested in several environments:
 
 - Windows, Linux, MacOS
-- Python 3.7
+- Python 3.6, 3.7, 3.8
+   - 3.8.0 and 3.8.1 only. Unfortunately, 3.8.2 has caused `nest_asyncio` to fail. Until that package is updated we are stuck at 3.8.1.
 - Jupyter Notebooks (not automated), regular python command-line invoked source files
 
 # Development

setup.py

@@ -19,7 +19,7 @@
       maintainer_email="gwatts@uw.edu",
       url="https://github.com/iris-hep/func_adl_xAOD",
       license="TBD",
-      python_requires='>=3.6',
+      python_requires='>=3.6, <=3.8.1',
       test_suite="tests",
       install_requires=[
           "pandas~=1.0",