made --loop work

so these two programs should be equivalent in functionality:
-	aws ec2 describe-instances | jsonp 'say $_->{PublicDnsName} foreach p("Reservations.*.Instances")'
-	aws ec2 describe-instances | jsonp --loop "Reservations.*.Instances" 'say p("PublicDnsName")'
HOWEVER the --loop version is going to be faster
-	this is because, when `jsonp` sees --loop, it knows to go ahead and slurp in all the input before trying to parse
while I was adding option processing, I went ahead and stuck in command line help (what the hey)