test: check examples in README

PR #146 
diff --git a/Cargo.toml b/Cargo.toml
index 3475bb0..17272e1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,7 @@
 [dev-dependencies]
 quickcheck = { version = "0.8", default-features = false }
 rand = "0.6"
+doc-comment = "0.3"
 
 [features]
 default = ["std"]
diff --git a/src/lib.rs b/src/lib.rs
index 0274d74..2ce9603 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -67,6 +67,13 @@
 #[cfg(feature = "std")]
 extern crate core;
 
+#[cfg(test)]
+#[macro_use]
+extern crate doc_comment;
+
+#[cfg(test)]
+doctest!("../README.md");
+
 use core::fmt::Debug;
 use core::hash::Hash;
 use core::ptr::copy_nonoverlapping;