Merge pull request sfackler#1080 from JamesGuthrie/patch-1

fix code block

Author: sfackler

postgres-types/src/lib.rs

@@ -168,6 +168,8 @@
 //!   'Happy'
 //! );
 //! ```
+//!
+//! ```rust
 //! #[postgres(allow_mismatch)]
 //! enum Mood {
 //!    Happy,