c++ -march=native -O3 -std=c++11 -o amalgamation_demo amalgamation_demo.cpp  && ./amalgamation_demo ../jsonexamples/twitter.json 

c++ -march=native -O3 -std=c++17 -o amalgamation_demo amalgamation_demo.cpp  && ./amalgamation_demo ../jsonexamples/twitter.json 

Fix the suggested command line to build to amalgamation_demo; it needs C++17 for string_view
Fix the suggested command line to build to amalgamation_demo; it needs C++17 for string_view
