Add a section describing how to setup ENS environment locally

[makoto]

We need a section describing how to setup ENS locally (eg: to ganache) and register some sample names.

Ideally using the followings

• https://truffleframework.com
• https://embark.status.im
• https://getwaffle.io
• web3.py/web3.j (no idea how it works though).

[makoto]

https://github.com/EthWorks/ENSBuilder allows you to deploy ENS locally as well

[Arachnid]

Done: https://ens.gitbook.io/ens/deploying-ens-on-a-private-chain

[makoto]

Please also mention how to specify the register the locally deployed address to the ENS library

[makoto]

V2 requires ensAddress at instantiation https://github.com/ensdomains/ensjs