fix: Disallow cloudpickle v1.5.0 in 'tensorflow' extra (#915)

* Explicitly disallow cloudpickle v1.5.0 to avoid breaking TensorFlow Probability 
   - This is a temporary solution to unblock development, but should be removed once TensorFlow Probability v0.11 has been released
   - tensorflow/probability#991
   - cloudpipe/cloudpickle#390

setup.py

@@ -1,7 +1,11 @@
 from setuptools import setup
 
 extras_require = {
-    'tensorflow': ['tensorflow~=2.0', 'tensorflow-probability~=0.8'],
+    'tensorflow': [
+        'tensorflow~=2.0',
+        'tensorflow-probability~=0.8',
+        'cloudpickle!=1.5.0',  # TODO: Temp patch until tfp v0.11
+    ],
     'torch': ['torch~=1.2'],
     'jax': ['jax~=0.1,>0.1.51', 'jaxlib~=0.1,>0.1.33'],
     'xmlio': ['uproot'],