Add tests for README file

Author: GuillaumeGomez

Cargo.toml

@@ -16,3 +16,6 @@ exclude = ["/.travis.yml", "/dev"]
 
 [badges]
 travis-ci = { repository = "dguo/strsim-rs" }
+
+[dev-dependencies]
+doc-comment = "0.3"

src/lib.rs

@@ -1,5 +1,12 @@
 //! This library implements string similarity metrics.
 
+#[cfg(test)]
+#[macro_use]
+extern crate doc_comment;
+
+#[cfg(test)]
+doctest!("../README.md");
+
 use std::char;
 use std::cmp::{max, min};
 use std::collections::HashMap;