Fix link to Mastodon's documentation

src/lib.rs

@@ -1,7 +1,6 @@
 //! # Elefren: API Wrapper around the Mastodon API.
 //!
-//! Most of the api is documented on [Mastodon's
-//! github](https://github.com/tootsuite/mastodon/blob/master/docs/Using-the-API/API.md#tag)
+//! Most of the api is documented on [Mastodon's website](https://docs.joinmastodon.org/api/)
 //!
 //! ```no_run
 //! # extern crate elefren;