Add measurement for extraction of AddSubmenu()

Author: kotfu

speedup_import.md

@@ -73,3 +73,13 @@ $ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
 100 iterations
 average: real 0.115 user 0.080 sys 0.020
 ```
+
+# extract AddSubmenu to its own file
+
+In commit ccfdf0f9 we extract AddSubmenu() to it's own file, so it is not
+imported or processed by default.
+```
+./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"100 iterations
+average: real 0.117 user 0.081 sys 0.021
+```
+