This commit also changes the signature of the 'ContentType'
'from_extension" method so that it returns an 'Option<ContentType>' as
opposed to 'ContentType'.
This commit also disallows negative quality values in 'Accept' media
types.
Modifying the `Rocket` structure just before launch doesn't make sense for
several reasons: 1) those affects can't influence the launch, and 2) they won't
be observed in tests. Thus, an `Attach` fairing kind was added that ameliorates
these issues.
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.
Sergio Benitez