Switching render_template to render_body.

The body element is re-used as a child element in blocks, so it makes more sense to make a function that renders that as opposed to a function that renders a top-level-only container that contains only a body.

src/parser/mod.rs

@@ -7,6 +7,7 @@ pub use node_invoker::run_node_dust;
 pub use node_invoker::NodeError;
 pub use node_invoker::Result;
 pub use parser::template;
+pub use parser::Body;
 pub use parser::DustTag;
 pub use parser::Template;
 pub use parser::TemplateElement;