Remove trailing semicolon from do_read macro

Fixes abonander#23

This will allow the macro to continue to be used in expression
position (e.g. match arms), where semicolons are not allowed.

src/policy.rs

@@ -22,7 +22,7 @@ pub struct DoRead(pub bool);
 /// Shorthand for `return DoRead(bool)` or `return DoRead(true)` (empty invocation)
 #[macro_export]
 macro_rules! do_read (
-    ($val:expr) => ( return $crate::policy::DoRead($val); );
+    ($val:expr) => ( return $crate::policy::DoRead($val) );
     () => ( do_read!(true); )
 );