Updated README.md for 1.6.4
Updated README.md for 1.6.4

Manual update.
aecepoglu/js-beautify,bitwiseman/js-beautify,jaichandra/js-beautify,beautify-web/js-beautify,mmsqe/js-beautify,Coburn37/js-beautify,beautify-web/js-beautify,Coburn37/js-beautify,aecepoglu/js-beautify,bitwiseman/js-beautify,Coburn37/js-beautify,jaichandra/js-beautify,bitwiseman/js-beautify,aecepoglu/js-beautify,mmsqe/js-beautify,bitwiseman/js-beautify,mmsqe/js-beautify,jaichandra/js-beautify,Coburn37/js-beautify,aecepoglu/js-beautify,jaichandra/js-beautify,beautify-web/js-beautify,mmsqe/js-beautify,beautify-web/js-beautify