Re-organize the consuming documentation for clarity

[jeremycline]

A number of users did not find the section on using a class as a
callback. This attempts to re-organize the documentation around the
consumer API to make it clearer.

@dustymabe, @bowlofeggs, it'd be great if you could skim this and let me know if it's clearer.

[dustymabe]

I think it would have helped me today if we add an example of calling that example class via the CLI. i.e. fedora-messaging --conf /work/my_config.toml consume --callback=modname:SaveMessage

[bowlofeggs]

LGTM!

[bowlofeggs]

Suggested change

	object as a single position argument.
	object as a single positional argument.

[jeremycline]

Fixed, thanks!

[codecov-io]

Codecov Report

Merging #177 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #177   +/-   ##
======================================
  Coverage    95.4%   95.4%           
======================================
  Files          14      14           
  Lines        1481    1481           
  Branches      198     198           
======================================
  Hits         1413    1413           
  Misses         51      51           
  Partials       17      17

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[jeremycline]

I think it would have helped me today if we add an example of calling that example class via the CLI. i.e. fedora-messaging --conf /work/my_config.toml consume --callback=modname:SaveMessage

I've added a note following the example class.

[dustymabe]

I think it would have helped me today if we add an example of calling that example class via the CLI. i.e. fedora-messaging --conf /work/my_config.toml consume --callback=modname:SaveMessage

I've added a note following the example class.

👍