How to install Nokogiri and lxml

How to install Nokogiri (Ruby) and lxml (Pyhon) with ease :

Install Nokogiri (ruby)

gem install nokogiri -- --use-system-libraries=true --with-xml2-include=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/libxml2

Install lxml (python)

brew install libxml2
brew install libxslt
brew link libxml2 --force
brew link libxslt --force
sudo pip install lxml
brew unlink libxml2
brew unlink libxslt