As Composer is now widely used in the PHP world, having to run composer
install before running the test suite is expected. This also has the
nice benefit of removing a bunch of code, making things easier to
maintain (there is only one place to declare a dev dependency), and
probably more.
HttpContentRenderer has been renamed to FragmentHandler.
The RendererStrategy subnamespace has been renamed to Fragment.
The strategy classes now have Fragment in their names.
ProxyRouterListener has been renamed to FragmentListener
The router_proxy configuration entry has been renamed to fragments.
The previous code allowed to pass null as a Request but that does not
really make sense as rendering a sub-request can only happen from a
master request. This was done to ease testing but that was a mistake.
