v0.16.3

This release adds an stop-gap fix to the Transact method so that it never
transfers value with the CallTx is generates.

We hard-code amount = fee so that no value is transferred
regardless of fee sent. This fixes an invalid jump destination error arising
from transferring value to non-payable functions with newer versions of solidity.
By doing this we can resolve some issues with users of the v0 RPC without making
a breaking API change.