Parse unsigned byte B in ValueReader

[ByteAlex]

Proposed Changes

This PR fixes #713 and implement's the type B as shown supported in this document.

Types of Changes

• Bugfix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
• Cosmetics (whitespace, appearance)

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works

Further Comments

Since this is a trivial change, I've not bothered to make the thing compile on my M1. As soon as I have my usual development environment available again, I'll run the tests and update this PR if necessary.

A question in regards to

I have added tests that prove my fix is effective or that my feature works

I have looked into the test files for the given method, but this method was not explicitly tested against all types, so I concluded that a test for my PR/fix would not be needed. Is that correct?