update gemspec to use ffi for binding to compiler
update gemspec to use ffi for binding to compiler

ruby-protobuf/protobuf,ruby-protobuf/protobuf,brianstien/protobuf,brianstien/protobuf,lookout/protobuffy,zanker/protobuf,film42/protobuf,lookout/protobuffy,quixoten/protobuf,quixoten/protobuf,zanker/protobuf,localshred/protobuf,film42/protobuf,localshred/protobuf