Fix 'clusure' typo in fairings guide and ad_hoc.rs.

Fixes #348.

lib/src/fairing/ad_hoc.rs

@@ -3,7 +3,7 @@ use fairing::{Fairing, Kind, Info};
 
 /// A ad-hoc fairing that can be created from a function or closure.
 ///
-/// This enum can be used to create a fairing from a simple function or clusure
+/// This enum can be used to create a fairing from a simple function or closure
 /// without creating a new structure or implementing `Fairing` directly.
 ///
 /// # Usage

site/guide/fairings.md

@@ -192,7 +192,7 @@ documentation](https://api.rocket.rs/rocket/fairing/trait.Fairing.html#example).
 
 For simple occasions, implementing the `Fairing` trait can be cumbersome. This
 is why Rocket provides the [`AdHoc`] type, which creates a fairing from a simple
-function or clusure. Using the `AdHoc` type is easy: simply call the
+function or closure. Using the `AdHoc` type is easy: simply call the
 `on_attach`, `on_launch`, `on_request`, or `on_response` constructors on `AdHoc`
 to create an `AdHoc` structure from a function or closure.