Use Laravel Str helpers for case changes

Advantage of the string helpers is that they are unicode-safe and adhere to the Laravel standard, thus maximizing compatibility in the future.

src/Sanitizers/Capitalize.php

@@ -3,6 +3,7 @@
 namespace ArondeParon\RequestSanitizer\Sanitizers;
 
 use ArondeParon\RequestSanitizer\Contracts\Sanitizer;
+use Illuminate\Support\Str;
 
 class Capitalize implements Sanitizer
 {
@@ -12,6 +13,6 @@ class Capitalize implements Sanitizer
      */
     public function sanitize($input)
     {
-        return ucfirst($input);
+        return Str::ucfirst($input);
     }
-}
+}

src/Sanitizers/Lowercase.php

@@ -3,6 +3,7 @@
 namespace ArondeParon\RequestSanitizer\Sanitizers;
 
 use ArondeParon\RequestSanitizer\Contracts\Sanitizer;
+use Illuminate\Support\Str;
 
 class Lowercase implements Sanitizer
 {
@@ -12,6 +13,6 @@ class Lowercase implements Sanitizer
      */
     public function sanitize($input)
     {
-        return strtolower($input);
+        return Str::lower($input);
     }
-}
+}

src/Sanitizers/Uppercase.php

@@ -3,6 +3,7 @@
 namespace ArondeParon\RequestSanitizer\Sanitizers;
 
 use ArondeParon\RequestSanitizer\Contracts\Sanitizer;
+use Illuminate\Support\Str;
 
 class Uppercase implements Sanitizer
 {
@@ -12,6 +13,6 @@ class Uppercase implements Sanitizer
      */
     public function sanitize($input)
     {
-        return strtoupper($input);
+        return Str::upper($input);
     }
-}
+}