[wsg] replace .for with .flatmap
[wsg] replace .for with .flatmap

The method .for is deprecated and will be removed in Rakudo 2015.09.  Its
replacement is .flatmap as corrected here.

Quinny/perl6-examples,stmuk/perl6-examples,Quinny/perl6-examples,perl6/perl6-examples,Quinny/perl6-examples,Quinny/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples,Quinny/perl6-examples,shlomif/perl6-examples,stmuk/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples