Fix warnings for unused attributes

src/lib.rs

@@ -77,6 +77,7 @@ mod reexport {
     pub use syntax::ast::{Name, NodeId};
 }
 
+#[allow(unused_attributes)]
 #[plugin_registrar]
 #[rustfmt_skip]
 pub fn plugin_registrar(reg: &mut Registry) {

src/misc.rs

@@ -365,6 +365,7 @@ impl LintPass for UsedUnderscoreBinding {
 }
 
 impl LateLintPass for UsedUnderscoreBinding {
+    #[allow(unused_attributes)]
     #[rustfmt_skip]
     fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
         if in_attributes_expansion(cx, expr) {