Explain how to create genesis file

[jackzampolin]

Currently the tutorial hand-waves over Genesis file creation and format. We need to add some more information about this. May bock on cosmos/cosmos-sdk#3006 or cosmos/cosmos-sdk#3406

[tac0turtle]

genesis file is auto created, I think we need a section in cosmos-sdk docs on how to construct it in app.go. Will close this issue for now

[0fatih]

@tac0turtle Have you guys created a section about it? Because I couldn't see.

If you don't, do you have any suggestions for me? I want to understand the parameters.