Change the name of the class to match the name exported from the package
index.

This should not be a breaking change because the class is the default
export of its module. Just in case there is some contrived case that
depends on the class's `name` attribute, we'll include this in the
v2.0.0 major release.

Jira: [ENG-2733]

The main point I wanted to add here is that this model is for _received_
messages. I've also added a bit of explanation about its intended use
with `SQSService`.

Jira: [ENG-2733]

Currently, sending an SQS message using `SQSService` does not throw an
error by default. This has caught us out a couple of times where we were
expecting a failure. The `failureMode` parameter was added to opt in to
throwing errors, to avoid introducing a breaking change in v1.

In v2 we'll throw errors by default, and you'll have to opt _out_ of
this behaviour.

BREAKING CHANGE: `SQSService#publish` throws by default instead of
handling errors. To maintain old behaviour, you can pass `"catch"` in
the `failureMode` parameter.