protobufjs@^6 triggers override mistake

[mhofman]

In Hardened JavaScript and similar environments the intrinsics are frozen for security.

protobufjs had an issue which triggered what is commonly known as the override mistake (using assignment to define a property which exists is unwritable in the prototype chain), in this case constructor of a custom Error.

That issue was fixed, but only as part of the ^7 major version. I'm not sure if there are breaking changes impacting this package, but updating protobufjs to the latest major would help projects using Hardened JS, like dapps building for the Agoric chain.

[webmaster128]

Thanks for bringing this up. I think we can even remove the protobufjs dependency entirely. See #79

[webmaster128]

Done in #79

[mhofman]

Even better, thanks!!