Release v5.0.0

Merge pull request keepkey#19 from keepkey/py3-multi-sig

Fix base58 functions and protobuf build

Update to v4.0.1 of device protocol

add support for v4.0.0 firmware, make it work with python3

Merge pull request keepkey#15 from keepkey/0.9.0

Bump to 0.9.0

Add version and lock_time parameters to sign_tx

Bump version to 0.8.0