[cgiapp] CAP::Dispatch do not support runmode with only one char as name

[silent]

Hi,

if I use only one char as run mode name, CAP-dispatch not work:

CAP-dispatch:
######
if($rm) {

# check runmode name
($rm) = ($rm =~ /^([a-zA-Z_][\w']+)$/);
throw_bad_request("Invalid characters in runmode name") unless $rm;
}
######

since we can use run mode like " sub z { ... }", I think it is better if
CAP-dispatch support it .