Improve wording in documentation (#83)

Remove redundant wording form documentation.

Port of https://github.com/tokio-rs/tokio-service/pull/30

tower-service/src/lib.rs

@@ -86,7 +86,7 @@ use std::sync::Arc;
 /// it is possible to write middleware that provide these pieces in a
 /// reusable way.
 ///
-/// For example, take timeouts as an example:
+/// Take timeouts as an example:
 ///
 /// ```rust,ignore
 /// use tower_service::Service;