Merge pull request opencontainers#253 from xiekeyang/typo

typo fix

layer.md

@@ -40,7 +40,7 @@ f60c56784b83/
         my-app-tools
 ```
 
-This example change is going add a configuration directory at `/etc/my-app.d` which contains a default config file.
+This example change is going to add a configuration directory at `/etc/my-app.d` which contains a default config file.
 There's also a change to the `my-app-tools` binary to handle the config layout change.
 The `f60c56784b83` directory then looks like this: