Bump dependencies.

package.json

@@ -15,17 +15,17 @@
 		"@wordpress/browserslist-config": "2.3.0",
 		"@wordpress/eslint-plugin": "2.1.0",
 		"babel-loader": "8.0.5",
-		"copy-webpack-plugin": "^6.0.3",
+		"copy-webpack-plugin": "^6.4.1",
 		"cross-env": "5.2.0",
 		"eslint": "5.16.0",
-		"grunt": "^1.0.4",
+		"grunt": "^1.3.0",
 		"grunt-checktextdomain": "^1.0.1",
 		"grunt-contrib-clean": "^1.1.0",
-		"grunt-contrib-compress": "^1.4.3",
+		"grunt-contrib-compress": "^1.6.0",
 		"grunt-contrib-copy": "^1.0.0",
 		"grunt-contrib-cssmin": "^2.2.1",
 		"grunt-force-task": "^2.0.0",
-		"grunt-rtlcss": "~2.0.1",
+		"grunt-rtlcss": "~2.0.2",
 		"grunt-text-replace": "^0.4.0",
 		"grunt-wp-i18n": "^1.0.3",
 		"grunt-wp-readme-to-markdown": "~1.0.0",