add some basic documentation to the backtrace capturing functionality to the README.
add some basic documentation to the backtrace capturing functionality to the README.

tuanthng/apitrace,schulmar/apitrace,tuanthng/apitrace,EoD/apitrace,joshua5201/apitrace,EoD/apitrace,joshua5201/apitrace,trtt/apitrace,surround-io/apitrace,joshua5201/apitrace,tuanthng/apitrace,trtt/apitrace,surround-io/apitrace,swq0553/apitrace,swq0553/apitrace,surround-io/apitrace,swq0553/apitrace,swq0553/apitrace,joshua5201/apitrace,tuanthng/apitrace,apitrace/apitrace,EoD/apitrace,apitrace/apitrace,schulmar/apitrace,schulmar/apitrace,schulmar/apitrace,tuanthng/apitrace,schulmar/apitrace,trtt/apitrace,surround-io/apitrace,apitrace/apitrace,trtt/apitrace,joshua5201/apitrace,apitrace/apitrace,EoD/apitrace,trtt/apitrace,EoD/apitrace,swq0553/apitrace,surround-io/apitrace