This is a breaking change.
The `testing` feature no longer exists. Testing structures can now be
accessed without any features enabled.
Prior to this change, Rocket would panic when draining from a network
stream failed. With this change, Rocket force closes the stream on any
error.
This change also ensures that the `Fairings` launch output only prints
if at least one fairing has been attached.
A few interesting notes on this breakage:
* `Cookie` how has a lifetime. It should be `'static'` everywhere.
* The `SetCookie` header is no longer reexported.
* Instead, `Cookie` implements `Into<Header>` for Set-Cookie.