[rosalind] handle default and command line input in fib example
[rosalind] handle default and command line input in fib example

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