make sure we buffer the entire input (backported from Plack a96a5b6)

otherwise, the app may read things before the Web::Request instance
does, and if the app doesn't buffer the input, then that data would not
be seen
fix uri escaping (backported from Plack 5f9c372)
add Web::Response->to_app (backported from Plack e3d0dde)
use Module::Runtime instead of Class::Load
changelog