Add "stdin: is not a tty warning" fix
Add Ruby and Node.js install functions

Moved each install section into a function. Added Ruby install code
using rbenv. Installs and sets Ruby 2.1.2 as the global default.
Installs some base gems including bundler, sass, and sass-globbing.
Node.js npm installs some base packages including yo, grunt-cli, bower,
and supervisor. Changed tab spacing from 4 to 2.