update appendix C++11 standards tutorial.
add nullptr explanation.
update std::initializer_list tutorial.
add uniform initializing syntax tutorial.
add alternative function syntax tutorial
fix writing.
update appendix C++11 standards.
update C++11 core language usability enhancements.md
update chapter1 web-resources.md
update chapter1 web-resources.md
add web-resources.
update chapter1 what is concurrency.
convert .jpg pic to .png
update chapter1 what is concurrency.
rename pic.
udpate chapter1 what is concurrency.
redrawing concurrent vs. parallel pic
udpate what is concurrency.
update What is concurrency.md
add two more pictures