Merge PR cosmos#1817: Add some instructions for rolling your testnet

cmd/gaia/testnets/README.md

@@ -473,3 +473,23 @@ You can also check your balance at a given block by using the `--block` flag:
 ```bash
 gaiacli account <account_cosmosaccaddr> --block=<block_height>
 ```
+
+## Create your Own Testnet
+
+To create your own testnet, first each validator will need to install gaiad and run gen-tx
+
+```bash
+gaiad init gen-tx --name <account_name>
+```
+
+This populations `$HOME/.gaiad/gen-tx/` with a json file.
+
+Now these json files need to be aggregated together via Github, a Google form, pastebin or other methods.
+
+Place all files on one computer in `$HOME/.gaiad/gen-tx/`
+
+```bash
+gaiad init --gen-txs -o --chain=<chain-name>
+```
+
+This will generate a `genesis.json` in `$HOME/.gaiad/config/genesis.json` distribute this file to all validators on your testnet.