Hardware wallet support

[mikeshultz]

Look into adding hardware wallet support. Or at least the major one or two.

[mikeshultz]

Ledger

• https://github.com/LedgerHQ/btchip-python
• https://github.com/LedgerHQ/blue-loader-python

[mikeshultz]

Started on this, but having issues getting the ledger to cooperate. When sending signed transactions with contract txdata, it would respond acting as if it needed more data after a full tx has been given. This might be on hold until Ledger drops a new debug firmware.

The old Dropbox link in the docs doesn't appear to be there anymore, so maybe this has been updated? The server link in these docs appears not to respond.

https://ledger.readthedocs.io/projects/blue-loader-python/en/latest/script_reference.html#updatefirmware-py

[mikeshultz]

Progress can be tracked in this project: https://github.com/mikeshultz/ledger-eth-lib