"Simple routes" - routes without a block

When a block isn't passed to the route invocation, render a template with the
same name as the route.

I hope you like the idea?

I was unsure about putting this on a separate line within the `route` method,
like this:

    block ||= proc { render path }

That would increase readability, but would add another LOC to the source.
I still opted for the current solution.