addHashableAttribute -> addHashable

Following pattern from addFillable()
Tidy up code

src/Database/Traits/Hashable.php

@@ -45,7 +45,7 @@ public static function bootHashable()
      * @param  array|string|null  $attributes
      * @return $this
      */
-    public function addHashableAttribute($attributes = null)
+    public function addHashable($attributes = null)
     {
         $attributes = is_array($attributes) ? $attributes : func_get_args();
 
@@ -105,4 +105,15 @@ public function getOriginalHashValue($attribute)
             ? $this->originalHashableValues[$attribute]
             : null;
     }
+
+    /**
+     * @deprecated use self::addHashable()
+     * Remove this method if year >= 2018
+     */
+    public function addHashableAttribute($attribute)
+    {
+        traceLog('The addHashableAttribute() method is deprecated, use addHashable() instead.');
+
+        return $this->addHashable($attribute);
+    }
 }

src/Database/Traits/Nullable.php

@@ -4,6 +4,11 @@
 
 trait Nullable
 {
+    /**
+     * @var array List of attribute names which should be set to null when empty.
+     *
+     * protected $nullable = [];
+     */
 
     /**
      * Boot the nullable trait for a model
@@ -25,9 +30,22 @@ public static function bootNullable()
         });
     }
 
+    /**
+     * Adds an attribute to the nullable attributes list
+     * @param  array|string|null  $attributes
+     * @return $this
+     */
+    public function addNullable($attributes = null)
+    {
+        $attributes = is_array($attributes) ? $attributes : func_get_args();
+
+        $this->nullable = array_merge($this->nullable, $attributes);
+
+        return $this;
+    }
+
     /**
      * Nullify empty fields
-     *
      * @return void
      */
     public function nullableBeforeSave()
@@ -43,5 +61,4 @@ public function nullableBeforeSave()
             }
         }
     }
-
 }

src/Database/Traits/Purgeable.php

@@ -41,7 +41,7 @@ public static function bootPurgeable()
      * @param  array|string|null  $attributes
      * @return $this
      */
-    public function addPurgeableAttribute($attributes = null)
+    public function addPurgeable($attributes = null)
     {
         $attributes = is_array($attributes) ? $attributes : func_get_args();