Separate Homebrew/MacPorts instructions for CMake + Ninja

Author: larryv

README.md

@@ -93,10 +93,13 @@ it next to the other projects and it will be bootstrapped automatically:
 
     git clone [email protected]:martine/ninja.git
 
-You can also use a third-party packaging tool like [Homebrew](http://brew.sh) or
-[MacPorts](https://macports.org) to install CMake and Ninja on OS X:
+You can also install CMake and Ninja on OS X using a third-party
+packaging tool like [Homebrew](http://brew.sh)…
 
     brew install cmake ninja
+
+…or [MacPorts](https://macports.org).
+
     sudo port install cmake ninja
 
 ### Building Swift