Update README, CONTRIBUTING for dev/rel branches

The `master` branch is now renamed to the `release` branch. Hopefully
this will alleviate the common issues of people submitting PRs to what
is essentiall our release branch.

CONTRIBUTING.md

@@ -12,14 +12,12 @@ improvements.
 
 Development Branches
 ---------------------
-We use `master` as our release branch. _Generally, changes should never go directly to the master
+We use `release` as our release branch. _Generally, changes should never go directly to the release
 branch_. All ongoing development work (and all of the latest changes) will be in the `dev` branch.
 However, we may want changes in other development branches (for example, in a `dev-patch` branch for
 a quick patch release). The appropriate target branch for any pull requests you want to make will be
 determined in the associated issue first (all PRs should have an associated issue).
 
-☞ _**Key Point: submitting a PR to `master` is almost always the wrong move.**_
-
 
 Issues
 -------
@@ -29,8 +27,7 @@ all kinds, even better ways to present something -- just go to the [issues page]
 **Before creating a new issue**, please review existing issues to see if someone has already
 submitted the same one. Chances are you're not the first to encounter something, so a little quick
 research can save everyone some hassle. It's also a good idea to verify that problems still exist in
-the development branch (which will be one of `dev-patch`, `dev-minor` or `dev-major`) when creating
-new issues.
+the development branch (`dev`) when creating new issues.
 
 When entering a new issue, please include all relevant information. For content issues, include the
 book or books this applies to, and specific locations that should be reviewed. Similarly for code:

README.md

@@ -117,10 +117,14 @@ languages (see [_Implementations in Other Languages_][implementations]), and acr
 operating systems. Feel free to add your own implementation to the list!
 
 ### Branches
-The `master` branch contains the latest released (and live) assets. In general, ongoing development,
-with all of the latest changes, can be found in the `dev` branch, which may contain patch, minor and
-major changes, depending on the release in progress. We try to keep CHANGELOG.md up to date, so you
-can easily browse what's new in each development branch.
+In general, ongoing development, with all of the latest changes, can be found in the `dev` branch,
+which may contain patch, minor and major changes, depending on the release in progress. We try to
+keep CHANGELOG.md up to date, so you can easily browse what's new in each development branch. We may
+from time to time use additional development branches, so stay up to date by reviewing the
+[CONTRIBUTING][] page.
+
+The `release` branch contains the latest released (and live) assets. This is the branch from which
+GitHub pages serves up https://raytracing.github.io/.
 
 
 Building and Running