removes default implementation of info

src/descriptors/mod.rs

@@ -2,9 +2,8 @@
 //! If two images are (almost) the same, their descriptions will be the same.
 
 pub trait Descriptor {
-    fn info(&self) -> String {
-        "Descriptor".to_string()
-    }
+    /// Print the name of the descriptor, 
+    fn info(&self) -> String;
     fn resize(&self, img: &image::DynamicImage) -> image::DynamicImage {
         img.grayscale().thumbnail_exact(8, 8)
     }