Made crate unsafe free and forbid unsafe

src/date.rs

@@ -356,7 +356,7 @@ impl fmt::Display for Rfc3339Timestamp {
         };
 
         // we know our chars are all ascii
-        f.write_str(unsafe { str::from_utf8_unchecked(&buf[..=offset]) })
+        f.write_str(str::from_utf8(&buf[..=offset]).expect("Conversion to utf8 failed"))
     }
 }
 

src/lib.rs

@@ -15,6 +15,7 @@
 //! [serde-humantime]: https://docs.rs/serde-humantime/0.1.1/serde_humantime/
 //! [humantime-serde]: https://docs.rs/humantime-serde
 
+#![forbid(unsafe_code)]
 #![warn(missing_debug_implementations)]
 #![warn(missing_docs)]