Go support for Protocol Buffers

Protocol buffers are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data, think XML, but smaller, faster, and simpler. You define how you want your data to be structured once, then you can use special generated source code to easily write and read your structured data to and from a variety of data streams and using a variety of languages. Protocol buffers currently support generated code in Java, Python, Objective-C, and C++. With our new proto3 language version, you can also work with Dart, Go, Ruby, and C#, with more languages to come. Package proto provides functions operating on protobuf messages such as cloning, merging, and checking equality, as well as binary serialization and text serialization. Package jsonpb serializes protobuf messages as JSON. Package ptypes provides helper functionality for protobuf well-known types.