docs: add note about multiprocessing usage (#26)

Author: crwilcox

docs/index.rst

@@ -1,5 +1,12 @@
 .. include:: README.rst
 
+.. note::
+
+ Because this client uses :mod:`grpcio` library, it is safe to
+ share instances across threads. In multiprocessing scenarios, the best
+ practice is to create client instances *after* the invocation of
+ :func:`os.fork` by :class:`multiprocessing.Pool` or
+ :class:`multiprocessing.Process`.
 
 Using the API
 -------------

noxfile.py

@@ -141,7 +141,7 @@ def docs(session):
  """Build the docs for this library."""
 
  session.install("-e", ".")
- session.install("sphinx", "alabaster", "recommonmark")
+ session.install("sphinx<3.0.0", "alabaster", "recommonmark")
 
  shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
  session.run(