.brew.sh: Automate switch to brew-installed Bash

Closes mathiasbynens#658.

Author: jeffbyrnes

bin/bash

@@ -26,6 +26,12 @@ brew install bash
 brew tap homebrew/versions
 brew install bash-completion2
 
+# Switch to using brew-installed bash as default shell
+if ! fgrep -q '/usr/local/bin/bash' /etc/shells; then
+  echo '/usr/local/bin/bash' | sudo tee -a /etc/shells;
+  chsh -s /usr/local/bin/bash;
+fi;
+
 # Install `wget` with IRI support.
 brew install wget --with-iri