Ganache-cli: Add support for eth_signTypedData

[rhlsthrm]

• I asked about this on gitter: [x]
• Link to my question on gitter: https://gitter.im/ConsenSys/truffle?at=5ae26c212b9dfdbc3ad31939

Expected Behavior

Support for eth_signTypedData from this EIP.

Current Behavior

Error message: Error: Method eth_signTypedData not supported.

[tal-beja]

+1

[vans163]

Yea

[fabioberger]

Any update on this?

[benjamincburns]

Copying my comment here from the PR:

I'm a little hesitant about this change, primarily because EIP-712 is still listed as draft status, and I can't find where either geth or Parity support it yet. I see that MetaMask has added support, however - so maybe that's good enough since most web apps will be interacting with the client via them or some other wallet middleware...

[benjamincburns]

OK, I'm walking back that comment a bit - I _really_ like the interaction this helps to support and I'd rather help move things forward by adding preliminary support for the RPC call.

[benjamincburns]

PR merged and will be released shortly - huge thanks to @rmeissner for saving us the hassle of implementing it ourselves! :heart: