docs/esp8266/tutorial: Make http_get sample function self contained.

docs/esp8266/tutorial/network_tcp.rst

@@ -61,6 +61,7 @@ of the request you need to specify the page to retrieve.
 Let's define a function that can download and print a URL::
 
     def http_get(url):
+        import socket
         _, _, host, path = url.split('/', 3)
         addr = socket.getaddrinfo(host, 80)[0][-1]
         s = socket.socket()
@@ -74,8 +75,7 @@ Let's define a function that can download and print a URL::
                 break
         s.close()
 
-Make sure that you import the socket module before running this function.  Then
-you can try::
+Then you can try::
 
     >>> http_get('http://micropython.org/ks/test.html')