Pass request to related serializers

Related serializers may need access to the request to properly serialize
a child resource.  For example, reverse() in djangorestframework.reverse
uses request if available to return an absolute URL.  While the parent
resource has access to the request to generate the absolute URL, the
child resource does not.

Small patch to allow RawQuerySet serialization

reverse takes `request` as a kwarg.

Okay, that looks good to me!

Related serializers passed in via include now work as expected.

This failing test shows that the serializer implementation breaks when a
related serializer is passed in via include rather than via fields.

Add exception handling to the XML parser

Custom reverse() and drop set_script_prefix

This fixes #167 except for the docs