add rbx back to the matrix
add rbx back to the matrix

i completely eliminated it before

h4ck3rm1k3/ffi-yajl,kou/ffi-yajl,h4ck3rm1k3/ffi-yajl,chef/ffi-yajl,chef/ffi-yajl,chef/ffi-yajl,kou/ffi-yajl,h4ck3rm1k3/ffi-yajl,kou/ffi-yajl