doc: update CONTRIBUTING.md

* Latest stable is v0.10 now.
* Add example of what the first line of the commit log should look like.

CONTRIBUTING.md

@@ -49,10 +49,10 @@ Okay, so you have decided on the proper branch.  Create a feature branch
 and start hacking:
 
 ```
-$ git checkout -b my-feature-branch -t origin/v0.8
+$ git checkout -b my-feature-branch -t origin/v0.10
 ```
 
-(Where v0.8 is the latest stable branch as of this writing.)
+(Where v0.10 is the latest stable branch as of this writing.)
 
 
 ### COMMIT
@@ -68,14 +68,15 @@ Writing good commit logs is important.  A commit log should describe what
 changed and why.  Follow these guidelines when writing one:
 
 1. The first line should be 50 characters or less and contain a short
-   description of the change.
+   description of the change prefixed with the name of the changed
+   subsystem (e.g. "net: add localAddress and localPort to Socket").
 2. Keep the second line blank.
 3. Wrap all other lines at 72 columns.
 
 A good commit log looks like this:
 
 ```
-Header line: explaining the commit in one line
+subsystem: explaining the commit in one line
 
 Body of commit message is a few lines of text, explaining things
 in more detail, possibly giving some background about the issue
@@ -99,7 +100,7 @@ Use `git rebase` (not `git merge`) to sync your work from time to time.
 
 ```
 $ git fetch upstream
-$ git rebase upstream/v0.8  # or upstream/master
+$ git rebase upstream/v0.10  # or upstream/master
 ```