Add a link to the usage page

Author: IvanUkhov

README.md

@@ -1,6 +1,7 @@
 # lapack-sys [![Package][package-img]][package-url] [![Documentation][documentation-img]][documentation-url] [![Build][build-img]][build-url]
 
-The package provides bindings to [LAPACK] (Fortran).
+The package provides bindings to [LAPACK] (Fortran). The usage of the package is
+explained [here][usage].
 
 ## Contribution
 
@@ -9,6 +10,7 @@ pull request. Note that any contribution submitted for inclusion in the project
 will be licensed according to the terms given in [LICENSE.md](LICENSE.md).
 
 [lapack]: https://en.wikipedia.org/wiki/LAPACK
+[usage]: https://blas-lapack-rs.github.io/usage
 
 [build-img]: https://travis-ci.org/blas-lapack-rs/lapack-sys.svg?branch=master
 [build-url]: https://travis-ci.org/blas-lapack-rs/lapack-sys

src/lib.rs

@@ -1,6 +1,9 @@
 //! Bindings to [LAPACK] (Fortran)
 //!
+//! The usage of the package is explained [here][usage].
+//!
 //! [lapack]: https://en.wikipedia.org/wiki/LAPACK
+//! [usage]: https://blas-lapack-rs.github.io/usage
 
 #![allow(non_camel_case_types)]
 #![no_std]