fix(review report): return readable image list in csv

The jsperf microbenchmark uses many other things. The string concatenation code there uses jquery which may be creating some additional temporary objects. So, I don't think this is a fair comparison. If there's a way we should write a fair microbenchmark to be sure. But anyway, Kevin tells me that he has changed it to use join. So, you win (even thought there is another needless array allocation on the stack).