Switch to relative imports

The relative imports make it clearer what code is within the project and where
it's coming from.

Migrate RequestContext users to render() calls.

This was necessary because render_to_response no longer takes a
context_instance. We were always using this to pass in a RequestContext,
which the render shortcut can already do, so switch to that.

Remove noop conservancy.context_processors imports.

You'll note this source doesn't exist in Git.
There's a reason for that.

Add sitefundgoal to top level view context.

The base template now has access to the fund-raising goal that will be
displayed site-wide. The view here must provide it in the context for
access everywhere.

Furthermore, we need a local context processor to make sure it's in
context everywhere, and we have to make sure that context is properly
passed along.

This code is a bit cargo-culted in, based on what I read in various
places about adding the Request context.

Just quit it with this relative import stuff.

While I think these relative imports seem to be valid for the running
application, I am having trouble with the django-admin applications
regarding them. I don't see this syntactic sugar as absolutely
essential, so I'm just going to change it now.