README: add more badges

Author: Jorge Aparicio

README.md

@@ -1,6 +1,6 @@
-[![Build Status][travis]](https://travis-ci.org/japaric/itm)
-
-[travis]: https://travis-ci.org/japaric/itm.svg?branch=master
+[![Build status](https://travis-ci.org/japaric/itm.svg?branch=master)](https://travis-ci.org/japaric/itm)
+[![crates.io](https://img.shields.io/crates/d/itm.svg)](https://crates.io/crates/itm)
+[![crates.io](https://img.shields.io/crates/v/itm.svg)](https://crates.io/crates/itm)
 
 # `itm`