Add description of device argument

README.md

@@ -218,6 +218,9 @@ This section lists all available constants and methods.
     -
         `axis` indicates an axis over which the function may perform its action.
         An axis is always given as a keyword argument.
+    -
+        `device` refers to a device on which a tensor can placed, which can
+        either be a framework-specific type or a string, e.g. `"cpu"`.
     -
         `ref` indicates a *reference tensor* from which properties, like its
         shape and data type, will be used. E.g., `zeros(tensor)` creates a 

requirements.txt

@@ -7,7 +7,7 @@ pytest-cov
 coveralls
 autograd>=1.3
 tensorflow>=2
-tensorflow_probability
+tensorflow-probability
 torch
 jax
 jaxlib