Add 'Building' section to README
Add 'Building' section to README

Links to install-idea-jars.sh and documents how to skip building the IntelliJ plugin
cushon/google-java-format,sormuras/google-java-format,cushon/google-java-format,sherter/google-java-format,sormuras/google-java-format,cushon/google-java-format,sormuras/google-java-format,meonlol/google-java-format,sherter/google-java-format,sherter/google-java-format,meonlol/google-java-format,meonlol/google-java-format