Move script lints to script_plugins

The plugins crate now just allows to hook into clippy from a single crate.

tests/compiletest/plugin/compile-fail/unrooted_must_root.rs

@@ -2,9 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#![feature(plugin)]
-#![plugin(plugins)]
 #![allow(dead_code)]
+#![feature(plugin)]
+#![plugin(script_plugins)]
 
 #[must_root]
 struct Foo {