Bug: middleware breaks view assertions by converting response content to string

[bakerkretzmar]

Using the middleware included in this package causes all response content to be plain strings instead of View objects, breaking lots of built-in test assertions like assertViewIs(), assertViewHas(), etc.

Happy to work on a PR if I have time, would be great if an issue could be opened for this or a note added to the docs so that users can be aware of this limitation.