feat!: replacing the isRunning method with status

[nicholasgriffintn]

Description:
Following on from #454, this removes the isRunning method in favour of a status method that returns both the running and polling state.

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?:
This would allow users to get the running and polling state from one method rather than creating multiple ways of getting this information, it can also be expanded in the future with more information.

This is a breaking change as it changes an existing method, outside of that, this change should not actually effect how the Consumer processes messages.

Code changes:

• Updated the README to document the old state and the removal of isRunning
• Added a new getStatus method to return the states
• Updated tests

[codeclimate]

Code Climate has analyzed commit 3946277 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 98.3% (0.0% change).

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