added note in get started to emphasize need to use up-to-date version…

…s and tools (docker#5311)

Signed-off-by: Victoria Bialas <victoria.bialas@docker.com>

get-started/part2.md

@@ -16,6 +16,11 @@ description: Learn how to write, build, and run a simple app -- the Docker way.
   docker run hello-world
   ```
 
+> **Tip**: Please use up-to-date Docker versions and clients to help the
+tutorial go swimmingly. For example, legacy apps like Docker Toolbox
+might give you unexpected results for local IP addresses and older
+versions of Docker do not support all features demo'ed here.
+
 ## Introduction
 
 It's time to begin building an app the Docker way. We'll start at the bottom of