docs: Fix out of date get_data() snippets

As of adc8fe3aed Receiver objects do not
have a get_data() method and Receiver.get() does not unpickle the
message.

docs/api.rst

@@ -677,7 +677,9 @@ Context Class
 
                 recv = context.call_async(os.check_output, 'ls /tmp/')
                 try:
-                    print recv.get_data()  # Prints output once it is received.
+                    # Prints output once it is received.
+                    msg = recv.get()
+                    print msg.unpickle()
                 except mitogen.core.CallError, e:
                     print 'Call failed:', str(e)
 

docs/getting_started.rst

@@ -170,11 +170,12 @@ It is a simple wrapper around the more flexible :meth:`Context.call_async`,
 which immediately returns a :class:`Receiver <mitogen.core.Receiver>` wired up
 to receive the return value instead. A receiver may simply be discarded, kept
 around indefinitely without ever reading its result, or used to wait on the
-results from several calls. Here :meth:`get_data() <mitogen.core.Receiver.get>`
+results from several calls. Here :meth:`get() <mitogen.core.Receiver.get>`
 is called to block the thread until the result arrives::
 
     >>> call = local.call_async(time.time)
-    >>> print call.get_data()
+    >>> msg = call.get()
+    >>> print msg.unpickle()
     1507292737.75547