added set operations example resolves issue #397
added set operations example
resolves issue #397

bfurtaw/thrust,bfurtaw/thrust,Vishwa07/thrust,allendaicool/thrust,malenie/thrust,google-code-export/thrust,google-code-export/thrust,levendlee/thrust,google-code-export/thrust,julianromera/thrust,Vishwa07/thrust,hemmingway/thrust,julianromera/thrust,rdmenezes/thrust,lishi0927/thrust,rdmenezes/thrust,bfurtaw/thrust,rdmenezes/thrust,lishi0927/thrust,h1arshad/thrust,hemmingway/thrust,UIKit0/thrust,allendaicool/thrust,allendaicool/thrust,hemmingway/thrust,google-code-export/thrust,h1arshad/thrust,malenie/thrust,Vishwa07/thrust,allendaicool/thrust,levendlee/thrust,malenie/thrust,julianromera/thrust,malenie/thrust,lishi0927/thrust,h1arshad/thrust,bfurtaw/thrust,hemmingway/thrust,UIKit0/thrust,levendlee/thrust,Vishwa07/thrust,UIKit0/thrust,UIKit0/thrust,h1arshad/thrust,julianromera/thrust,levendlee/thrust,lishi0927/thrust,rdmenezes/thrust