Preserve underscores in Constantize function
Preserve underscores in Constantize function

Fixes #56.

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