Removed deprecated Str trait.

Author: SSheldon

src/object.rs

@@ -76,7 +76,7 @@ mod tests {
         let obj = NSObject::new();
         let description = obj.description();
         let expected = format!("<NSObject: {:p}>", &*obj);
-        assert!(description.as_str() == expected.as_slice());
+        assert!(description.as_str() == &*expected);
     }
 
     #[test]

src/string.rs

@@ -69,12 +69,6 @@ impl INSCopying for NSString {
     type Output = NSString;
 }
 
-impl Str for NSString {
-    fn as_slice(&self) -> &str {
-        self.as_str()
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::{INSCopying, INSString, NSString};