/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

$ brew update
$ brew install rbenv

# list all available versions:
$ rbenv install -l

# install a Ruby version:
$ rbenv install 2.2.2
# check already install ruby verison
$ rbenv vesions

$ gem install bundler

source 'https://rubygems.org'
gem 'capybara'

$ bundle install

Errno::EACCES: Permission denied @ rb_sysopen - /Users/lqi/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/nokogiri-1.7.1/.autotest
Using rack-test 0.6.3
Using childprocess 0.6.3
An error occurred while installing nokogiri (1.7.1), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.7.1'` succeeds before bundling.

$ xcode-select --install

$ sudo gem install nokogiri -v '1.7.1'

$ bundle install