Rewrite summary for contributing to a project

Closes #692

Author: HonkingGoose

book/05-distributed-git/sections/contributing.asc

@@ -787,6 +787,11 @@ Result: OK
 
 ==== Summary
 
-This section has covered a number of common workflows for dealing with several very different types of Git projects you're likely to encounter, and introduced a couple of new tools to help you manage this process.
+We covered multiple workflows, and talked about the differences between working as part of a small team on closed-source projects vs contributing to a big public project.
+You know to check for white-space errors before committing, and can write a great commit message.
+You learned how to format patches, and e-mail them to a developer mailing list.
+Dealing with merges was also covered in the context of the different workflows.
+You are now well prepared to collaborate on any project.
+
 Next, you'll see how to work the other side of the coin: maintaining a Git project.
 You'll learn how to be a benevolent dictator or integration manager.