Adds simple delete api

cookbook/src/lib.rs

@@ -30,6 +30,16 @@ pub mod recipes {
         recipes.load::<Recipe>(conn)
             .expect("Error loading recipe's list")
     }
+
+    pub fn delete(conn: &SqliteConnection, recipe_id: i32) -> bool {
+        use self::schema::recipes::dsl::*;
+
+        diesel::delete(
+                recipes.filter(
+                    id.eq(recipe_id)))
+            .execute(conn)
+            .is_ok()
+    }
 }