Fix compile error

Author: notriddle

src/book/init.rs

@@ -152,7 +152,7 @@ impl BookBuilder {
         js.write_all(theme::JS)?;
 
         let syntax_dir = cssdir.join("syntax");
-        fs::create_dir_all(syntax_dir)?;
+        fs::create_dir_all(&syntax_dir)?;
 
         let mut highlight_css = File::create(syntax_dir.join("light.css"))?;
         highlight_css.write_all(theme::SYNTAX_LIGHT_CSS)?;