Update Utterance Feature (Expose Variable, Logging, etc)

[dvonthenen]

Proposed changes

This adds onto the #147 PR.

Changes include:

• Exposing the UtteranceEndMs variable to set the feature
• Changed some of the trace messages so they aren't so chatty when debugging this feature
• Adds onto the Use fmt Instead of log for Examples PR Use fmt Instead of log for Examples #148

Types of changes

What types of changes does your code introduce to the community Go SDK?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update or tests (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

Tested all examples to make sure they work!