Update README.md

README.md

@@ -13,7 +13,7 @@ Please make sure you use the **latest nightly** of `rustc` before building (for
 [![Travis Build Status](https://travis-ci.org/redox-os/redox.svg?branch=master)](https://travis-ci.org/redox-os/redox)
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-![Rust Version](https://img.shields.io/badge/rust-nightly%202017--04--18-lightgrey.svg)
+![Rust Version](https://img.shields.io/badge/rust-nightly%202017--04--22-lightgrey.svg)
 
 ## Contents