Move admin.css select2 dependency to gruntfile

Gruntfile.js

@@ -154,11 +154,21 @@ module.exports = function( grunt ) {
 			}
 		},
 
+		// Concatenate select2.css onto the admin.css files.
+		concat: {
+			admin: {
+				files: {
+					'<%= dirs.css %>/admin.css' : ['<%= dirs.css %>/select2.css', '<%= dirs.css %>/admin.css'],
+					'<%= dirs.css %>/admin-rtl.css' : ['<%= dirs.css %>/select2.css', '<%= dirs.css %>/admin-rtl.css']
+				}
+			},
+		},
+
 		// Watch changes for assets.
 		watch: {
 			css: {
 				files: ['<%= dirs.css %>/*.scss'],
-				tasks: ['sass', 'cssmin']
+				tasks: ['sass', 'rtlcss', 'cssmin', 'concat']
 			},
 			js: {
 				files: [
@@ -280,6 +290,7 @@ module.exports = function( grunt ) {
 	grunt.loadNpmTasks( 'grunt-contrib-uglify' );
 	grunt.loadNpmTasks( 'grunt-contrib-sass' );
 	grunt.loadNpmTasks( 'grunt-contrib-cssmin' );
+	grunt.loadNpmTasks( 'grunt-contrib-concat' );
 	grunt.loadNpmTasks( 'grunt-contrib-watch' );
 	grunt.loadNpmTasks( 'grunt-contrib-clean' );
 	grunt.loadNpmTasks( 'grunt-stylelint' );
@@ -301,7 +312,8 @@ module.exports = function( grunt ) {
 	grunt.registerTask( 'css', [
 		'sass',
 		'rtlcss',
-		'cssmin'
+		'cssmin',
+		'concat'
 	]);
 
 	grunt.registerTask( 'docs', [

assets/css/admin.scss

@@ -11,7 +11,6 @@
 @import 'mixins';
 @import 'variables';
 @import 'animation';
-@import 'select2';
 @import 'fonts';
 
 /**

package.json

@@ -23,6 +23,7 @@
     "grunt-stylelint": "^0.6.0",
     "grunt-wp-i18n": "~0.5.4",
     "grunt-rtlcss": "2.0.1",
+    "grunt-contrib-concat": "1.0.1",
     "node-bourbon": "~4.2.3"
   },
   "engines": {