replace client link in docs

fixes issue hyperium#3453

src/client/conn/mod.rs

@@ -5,8 +5,8 @@
 //! are not handled at this level. This module provides the building blocks to
 //! customize those things externally.
 //!
-//! If don't have need to manage connections yourself, consider using the
-//! higher-level [Client](super) API.
+//! If you are looking for a convenient HTTP client,
+//! then you may wish to consider [reqwest](https://github.com/seanmonstar/reqwest).
 //!
 //! ## Example
 //!