Make it possible to access request objects in templates.

In Django, it is possible to access the request object in templates by adding the proper context processor (https://docs.djangoproject.com/en/dev/ref/templates/api/#django-core-context-processors-request). I don't know how to implement this more generally in ChicagoBoss, but here's an attempt at a specific way to do it. It means a setting will be required to use it (as with Django), but it is not a generic context processor replacement. If there's a better way, I'd be very interested to learn more about it.

Briefly tested and seems to work.