update bearer documentation

src/lib.rs

@@ -103,6 +103,27 @@
 //! # }
 //! ```
 //!
+//! ### Using bearer access tokens
+//!
+//! Bearer tokens can be converted to Hyper headers.
+//!
+//! ```no_run
+//! # extern crate inth_oauth2;
+//! # extern crate reqwest;
+//! # use inth_oauth2::Client;
+//! # use inth_oauth2::provider::google::Installed;
+//! use inth_oauth2::Token;
+//!
+//! # fn main() {
+//! # let oauth_client = Client::new(Installed, String::new(), String::new(), None);
+//! # let http = reqwest::Client::new();
+//! # let token = oauth_client.request_token(&http, "").unwrap();
+//! let request = http.get("https://example.com/resource")
+//!     .bearer_auth(token.access_token())
+//!     .build();
+//! # }
+//! ```
+//!
 //! ### Persisting tokens
 //!
 //! All token types implement `Serialize` and `Deserialize` from `serde`.