Update README [skip ci]

Author: termoshtt

README.md

@@ -4,30 +4,32 @@ ndarray-linalg
 [![docs.rs](https://docs.rs/ndarray-linalg/badge.svg)](https://docs.rs/ndarray-linalg)
 [![wercker status](https://app.wercker.com/status/f04aeba682ea6e79577e15bd946344a5/s/master "wercker status")](https://app.wercker.com/project/byKey/f04aeba682ea6e79577e15bd946344a5)
 
-Linear algebra package for Rust.
+Linear algebra package for Rust with [rust-ndarray](https://github.com/bluss/rust-ndarray).
 
-Dependencies
--------------
+LAPACKE Backend
+----------------
 
-- [bluss/rust-ndarray](https://github.com/bluss/rust-ndarray)
-- [blas-lapack-rs/lapacke](https://github.com/blas-lapack-rs/lapacke)
-
-and more (See Cargo.toml).
-
-Choosing LAPACKE implementation
---------------------------------
-
-For the sake of linking flexibility, you must provide LAPACKE implementation (as an `extern crate`) yourself.
 Currently three LAPACKE implementations are supported and tested:
 
 - [OpenBLAS](https://github.com/cmr/openblas-src)
 - [Netlib](https://github.com/cmr/netlib-src)
 - [Intel MKL](https://github.com/termoshtt/rust-intel-mkl) (non-free license, see the linked page)
 
+There are two ways to link LAPACKE backend:
+
+### backend features (recommended)
+There are three features corresponding to the backend implementations (`openblas` / `netlib` / `intel-mkl`):
+
+```toml
+[depencdencies]
+ndarray = "0.10"
+ndarray-linalg = { version = "0.8", features = ["openblas"] }
+```
+
+### link backend crate manually
+For the sake of linking flexibility, you can provide LAPACKE implementation (as an `extern crate`) yourself.
 You should link a LAPACKE implementation to a final crate (like binary executable or dylib) only, not to a Rust library.
-Example:
 
-`Cargo.toml`:
 ```toml
 [depencdencies]
 ndarray = "0.10"
@@ -36,13 +38,25 @@ openblas-src = "0.5" # or another backend of your choice
 
 ```
 
-`main.rs`:
+You must add `extern crate` to your code in this case:
+
 ```rust
 extern crate ndarray;
 extern crate ndarray_linalg;
 extern crate openblas_src; // or another backend of your choice
 ```
 
+### For librarian
+If you creating a library depending on this crate, we encourage you not to link any backend for flexibility:
+
+```toml
+[depencdencies]
+ndarray = "0.10"
+ndarray-linalg = { version = "0.8", default-features = false }
+```
+
+However, if you hope simplicity instead of the flexibility, you can link your favorite backend in the way described above.
+
 Examples
 ---------
 See [examples](https://github.com/termoshtt/ndarray-linalg/tree/master/examples) directory.