 
 For example, here is the trivial `identity` filter:
 
-    let identity = Filter { (box: MustacheBox, _) in
+    let identity = Filter { (box: MustacheBox) in
         return box
     }
 
-    let template = Template(string: "{{identity(a)}}, {{identity(b)}}")!
+    let template = try! Template(string: "{{identity(a)}}, {{identity(b)}}")
     template.registerInBaseContext("identity", Box(identity))
 
     // "foo, 1"
-    template.render(Box(["a": "foo", "b": 1]))!
+    try! template.render(Box(["a": "foo", "b": 1]))
 
 If the template provides more than one argument, the filter returns an error of
 domain `GRMustacheErrorDomain` and code `GRMustacheErrorCodeRenderingError`.

        }
    }

    let template = Template(string: "{{value}}")!
    let rendering = template.render(Box(["value": Box(renderValue)]))!

- parameter info:   A RenderingInfo
- parameter error:  If there is a problem in the rendering, upon return contains an

        "fullName": Box(fullName)]

    // Renders "Lionel Richie has a Mustache."
    let rendering = try! template.render(Box(data))

Warning: the returned String is *parsed* each time the lambda is executed. In
the example above, this is inefficient because the same
