Add option to opt-out of auto-parsing JSON

[mk-pmb]

Just discovered the JSON auto-parsing feature in src/compat-node-amqp.coffee. There should be an opt-out so people can process messages whose contentType is lying.

[fred-o]

That sound totally reasonable. I'm thinking about whether this should be a global option for the whole client object.

[mk-pmb]

It's been annoying for a while now. :-( Do you intend to fix this any time soon?
If in doubt, add the opt-out option where it has least impact on legacy code, e.g. at the .subscribe() call.

[mk-pmb]

Any news on this one?