contributing: wrap lines for readability

CONTRIBUTING.md

@@ -1,27 +1,42 @@
 ## Pull request procedure
 
-Pull requests should be targeted at Rust's `incoming` branch (note that by default Github will aim them at the `master` branch) --
-see "Changing The Commit Range and Destination Repository" in Github's documentation on [pull requests](https://help.github.com/articles/using-pull-requests).
-Before pushing to your Github repo and issuing the pull request, please do two things:
+Pull requests should be targeted at Rust's `incoming` branch (note
+that by default Github will aim them at the `master` branch) -- see
+"Changing The Commit Range and Destination Repository" in Github's
+documentation on [pull
+requests](https://help.github.com/articles/using-pull-requests).
+Before pushing to your Github repo and issuing the pull request,
+please do two things:
 
-1. [Rebase](http://git-scm.com/book/en/Git-Branching-Rebasing) your local changes against the `incoming` branch. Resolve any conflicts that arise.
-2. Run the full Rust test suite with the `make check` command.
-You're not off the hook even if you just stick to documentation; code examples in the docs are tested as well!
+1. [Rebase](http://git-scm.com/book/en/Git-Branching-Rebasing) your
+   local changes against the `incoming` branch. Resolve any conflicts
+   that arise.
 
-Pull requests will be treated as "review requests",
-and we will give feedback we expect to see corrected on [style](https://github.com/mozilla/rust/wiki/Note-style-guide) and substance before pulling.
-Changes contributed via pull request should focus on a single issue at a time, like any other.
-We will not accept pull-requests that try to "sneak" unrelated changes in.
+2. Run the full Rust test suite with the `make check` command.  You're
+   not off the hook even if you just stick to documentation; code
+   examples in the docs are tested as well!
 
-Normally, all pull requests must include regression tests (see [Note-testsuite](https://github.com/mozilla/rust/wiki/Note-testsuite)) that test your change.
-Occasionally, a change will be very difficult to test for.
-In those cases, please include a note in your commit message explaining why.
+Pull requests will be treated as "review requests", and we will give
+feedback we expect to see corrected on
+[style](https://github.com/mozilla/rust/wiki/Note-style-guide) and
+substance before pulling.  Changes contributed via pull request should
+focus on a single issue at a time, like any other.  We will not accept
+pull-requests that try to "sneak" unrelated changes in.
 
-In the licensing header at the beginning of any files you change, please make sure the listed date range includes the current year.
-For example, if it's 2013, and you change a Rust file that was created in 2010, it should begin:
+Normally, all pull requests must include regression tests (see
+[Note-testsuite](https://github.com/mozilla/rust/wiki/Note-testsuite))
+that test your change.  Occasionally, a change will be very difficult
+to test for.  In those cases, please include a note in your commit
+message explaining why.
+
+In the licensing header at the beginning of any files you change,
+please make sure the listed date range includes the current year.  For
+example, if it's 2013, and you change a Rust file that was created in
+2010, it should begin:
 
 ```
 // Copyright 2010-2013 The Rust Project Developers.
 ```
 
-For more details, please refer to [Note-development-policy](https://github.com/mozilla/rust/wiki/Note-development-policy).
+For more details, please refer to
+[Note-development-policy](https://github.com/mozilla/rust/wiki/Note-development-policy).