Install io.js & add aliases to switch to io/node

* Install `io.js`.
  https://iojs.org/en/index.html

* Add aliases to easily switch between `io.js` and `Node.js`.
  https://gist.github.com/phelma/ce4eeeedb8fb9a9e8e63

.aliases

@@ -139,3 +139,7 @@ alias afk="/System/Library/CoreServices/Menu\ Extras/User.menu/Contents/Resource
 
 # Reload the shell (i.e. invoke as a login shell)
 alias reload="exec $SHELL -l"
+
+# Easily switch between `io.js` and `Node.js`
+alias use-iojs="brew unlink node && brew link --force iojs"
+alias use-node="brew unlink iojs && brew link --force node"

brew.sh

@@ -98,5 +98,8 @@ brew install zopfli
 # installation method.
 brew install node
 
+# Install io.js
+brew install iojs
+
 # Remove outdated versions from the cellar.
 brew cleanup