Consider adding section explaining LCD / FCD

[peterpme]

Hi there,

I'm at the Terra Hackathon in Chicago and this question has come up a couple times:

• What is FCD?
• What is the difference between LCD and FCD?

I understand that LCD stands for "Light Client Daemon"? but besides considering it a thin javascript wrapper for making API calls, I'm not quite sure what it's doing.

It would be very helpful to add a "What is FCD? How is it different than LCD?" at the bottom of the readme to help newcomers understand better.

Thanks!