Add note about include and blocks; update wrapping of templating docs.
Add note about include and blocks; update wrapping of templating docs.

oddbird/nunjucks,internalfx/nunjucks,devoidfury/nunjucks,mozilla/nunjucks,internalfx/nunjucks,mozilla/nunjucks,oddbird/nunjucks,kevinschaul/nunjucks,internalfx/nunjucks,oddbird/nunjucks,oddbird/nunjucks,devoidfury/nunjucks,devoidfury/nunjucks,kevinschaul/nunjucks,kevinschaul/nunjucks,internalfx/nunjucks,mozilla/nunjucks,kevinschaul/nunjucks