Add crates.io and docs.rs links to readme

Author: dfaust

README.md

@@ -1,8 +1,9 @@
 # Multi-Map
 
 [![Build Status](https://travis-ci.org/thejpster/multi-map.svg?branch=master)](https://travis-ci.org/thejpster/multi-map)
+[![Crate version](https://img.shields.io/crates/v/multi-map.svg)](https://crates.io/crates/multi-map)
+[![Documentation](https://img.shields.io/badge/documentation-docs.rs-df3600.svg)](https://docs.rs/multi-map)
 
-Like a std::collection::HashMap, but allows you to use either of two different keys to retrieve items.
+Like a `std::collection::HashMap`, but allows you to use either of two different keys to retrieve items.
 
 For more details, see [the Github.io page](http://thejpster.github.io/multi-map/).
-