add check for yajl-ruby vulnerability
add check for yajl-ruby vulnerability

it looks like this code is not vulnerable

Signed-off-by: Lamont Granquist <0ab8dc438f73addc98d9ad5925ec8f2b97991703@scriptkiddie.org>

chef/ffi-yajl,chef/ffi-yajl,chef/ffi-yajl