silverstripe 4 compatibility

_config.php

@@ -1,3 +1,3 @@
 <?php
 
-define('FONT_AWESOME_DIR', ltrim(Director::makeRelative(realpath(__DIR__)), DIRECTORY_SEPARATOR));
+define('FONT_AWESOME_DIR', ltrim(\SilverStripe\Control\Director::makeRelative(realpath(__DIR__)), DIRECTORY_SEPARATOR));

code/extensions/FontAwesomeControllerExtension.php

@@ -1,5 +1,8 @@
 <?php
 
+use SilverStripe\Core\Extension;
+use SilverStripe\View\Requirements;
+
 /**
  * Class FontAwesomeControllerExtension
  */

code/formfields/FontAwesomeField.php

@@ -1,5 +1,10 @@
 <?php
 
+namespace SilverStripe\FontAwesome;
+
+use SilverStripe\Forms\TextField;
+use SilverStripe\View\Requirements;
+
 /**
  * Class FontAwesomeField
  */
@@ -23,7 +28,6 @@ class FontAwesomeField extends TextField
         $this->addExtraClass('form-control icp icp-auto');
 
         //Libraries
-        Requirements::css(FONT_AWESOME_DIR . '/css/lib/bootstrap.min.css');
         Requirements::css(FONT_AWESOME_DIR . '/css/lib/font-awesome.min.css');
         Requirements::css(FONT_AWESOME_DIR . '/css/lib/font-awesome-iconpicker.min.css');
         Requirements::javascript(FONT_AWESOME_DIR . '/js/lib/font-awesome-iconpicker.min.js');

css/font-awesome-module.css

@@ -1,9 +1,3 @@
-* {
-    -webkit-box-sizing: content-box;
-    -moz-box-sizing: content-box;
-    box-sizing: content-box;
-}
-
 .iconpicker-popover.popover {
     width: 512px;
 }