Improved error messages & visibility

[spluxx]

Suggested by @DoneSpeak #13

Errors like index out of range: 128 + 10 > 128 is somewhat cryptic, but it seems like the main library considers it sufficient. protobufjs/protobuf.js#691 (comment)

In a high-level view, the protobuf-related logic consists of 4 components.

1. parsing .proto files
2. binary <-> object
3. object <-> view model
4. view model <-> view

1 and 2 are done through protobufjs, so I think we can just build a lightweight module that takes in a protobufjs error and returns a more friendly error.

3, if it fails for some unexpected reason, we should still display the object rather than just giving up, so that the users can debug the issue.