fixed typos in comments (#89)

tower-balance/src/load/instrument.rs

@@ -4,7 +4,7 @@ use futures::{Future, Poll};
 ///
 /// This utility allows load metrics to have a protocol-agnostic means to track streams
 /// past their initial response future. For example, if `V` represents an HTTP response
-/// type, an implementaton could add `H`-typed handles to each response's extensions to
+/// type, an implementation could add `H`-typed handles to each response's extensions to
 /// detect when the response is dropped.
 ///
 /// Handles are intended to be RAII guards that primarily implement `Drop` and update load

tower-util/src/boxed.rs

@@ -1,8 +1,8 @@
 //! Trait object `Service` instances
 //!
 //! Dynamically dispatched `Service` objects allow for erasing the underlying
-//! `Service` type and using the `Service` intances as opaque handles. This can
+//! `Service` type and using the `Service` instances as opaque handles. This can
-//! be useful when the service instance cannot be explictly named for whatever
+//! be useful when the service instance cannot be explicitly named for whatever
 //! reason.
 //!
 //! There are two variants of service objects. `BoxService` requires both the