Highlight the CLI usage example as a shell session

cheroot/cli.py

@@ -1,24 +1,26 @@
 """Command line tool for starting a Cheroot WSGI/HTTP server instance.
 
-Basic usage::
+Basic usage:
 
-    # Start a server on 127.0.0.1:8000 with the default settings
-    # for the WSGI app myapp/wsgi.py:application()
-    cheroot myapp.wsgi
+.. code-block:: shell-session
 
-    # Start a server on 0.0.0.0:9000 with 8 threads
-    # for the WSGI app myapp/wsgi.py:main_app()
-    cheroot myapp.wsgi:main_app --bind 0.0.0.0:9000 --threads 8
+    $ # Start a server on 127.0.0.1:8000 with the default settings
+    $ # for the WSGI app myapp/wsgi.py:application()
+    $ cheroot myapp.wsgi
 
-    # Start a server for the cheroot.server.Gateway subclass
-    # myapp/gateway.py:HTTPGateway
-    cheroot myapp.gateway:HTTPGateway
+    $ # Start a server on 0.0.0.0:9000 with 8 threads
+    $ # for the WSGI app myapp/wsgi.py:main_app()
+    $ cheroot myapp.wsgi:main_app --bind 0.0.0.0:9000 --threads 8
 
-    # Start a server on the UNIX socket /var/spool/myapp.sock
-    cheroot myapp.wsgi --bind /var/spool/myapp.sock
+    $ # Start a server for the cheroot.server.Gateway subclass
+    $ # myapp/gateway.py:HTTPGateway
+    $ cheroot myapp.gateway:HTTPGateway
 
-    # Start a server on the abstract UNIX socket CherootServer
-    cheroot myapp.wsgi --bind @CherootServer
+    $ # Start a server on the UNIX socket /var/spool/myapp.sock
+    $ cheroot myapp.wsgi --bind /var/spool/myapp.sock
+
+    $ # Start a server on the abstract UNIX socket CherootServer
+    $ cheroot myapp.wsgi --bind @CherootServer
 
 .. spelling::