Clarified recommended Mac setup method

BUILD_GUIDE.md

@@ -6,13 +6,15 @@
 What these instructions look like depends on whether NoahAndrews's setup scripts get merged
 
 ### Mac
-If you're using homebrew, you can use the following commands:
+If you're using [homebrew,](http://brew.sh/) you can use the following commands:
 
     brew tap osx-cross/avr
     brew install avr-libc
     brew install dfu-programmer
 
-Otherwise, these instructions will work:
+This is the recommended method. If you don't have homebrew, [install it!](http://brew.sh/) It's very much worth it for anyone who works in the command line.
+
+You can also try these instructions:
 
 1. Install Xcode from the App Store.
 2. Install the Command Line Tools from `Xcode->Preferences->Downloads`.