Add C++ Protobuf example

[jtbandes]

We should provide example code for using Protobuf encoding in C++.

This will also require importing or adding our own base64 encoding implementation.

[felixf4xu]

please~

We are using python but for some online data visualization (10Hz and 20Hz or even higher), python's performance is now a bottleneck.

[felixf4xu]

I'm using https://gist.github.com/tomykaira/f0fd86b6c73063283afe550bc5d77594 for base64 encoding