feat: adding the ability to update visibilityTimeout

[nicholasgriffintn]

Resolves #370

Description:

As described in the feature request, this PR will add the ability for users to programatically update options for the Consumer. At the moment, this has only been configured with the ability to update visibilityTimeout, but in a way that'll be expandable in the future.

Type of change:

• Bug fix (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 change)

Why is this change required?:

When an external factor occurs, users may want to trigger an update to the visibilityTimeout option that will take effect from that point on.

Rather than stopping and then restarting the Consumer, they would like to do this in the current instance.

Code changes:

• Added a new public method .updateOption(), this will take an option and a value and then update the provided option with the provided value
• Updated documentation around this

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Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codeclimate]

Code Climate has analyzed commit 6bb1910 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (80% is the threshold).

This pull request will bring the total coverage in the repository to 94.7% (0.2% change).

View more on Code Climate.