WARNING: Nokogiri was built against LibXML version 2.8.0, but has dynamically loaded 2.9.0

Copied from https://github.com/sparklemotion/nokogiri/issues/742

Moved gem 'nokogiri' in the Gemfile to the top (just below gem 'rails') then:

brew uninstall libxml2
gem uninstall nokogiri
gem install nokogiri