Test inlining

Drawing analogy from [sidekiq testing by inlining](https://github.com/mperham/sidekiq/wiki/Testing#testing-workers-inline),
`sidekiq-status` allows to bypass redis and return a stubbed `:complete` status.
Since inlining your sidekiq worker will run it in-process, any exception it throws will make your test fail.
It will also run synchronously, so by the time you get to query the job status, the job will have been completed
successfully.
In other words, you'll get the `:complete` status only if the job didn't fail.

Inlining example:

You can run Sidekiq workers inline in your tests by requiring the `sidekiq/testing/inline` file in your `{test,spec}_helper.rb`:

`require 'sidekiq/testing/inline'`

To use `sidekiq-status` inlining, require it too in your `{test,spec}_helper.rb`:

`require 'sidekiq-status/testing/inline'`