Use nightly Rust in Travis CI config snippet

The current stable rustfmt (rustfmt 0.4.1-stable) does not contain
the `--check` flag, which is used in the Travis config snippet.
Once a new stable version is released, the snippet can be switched
back to stable Rust.

diff --git a/README.md b/README.md
index 051820010d3d3eaaff956da4ea179fc9fbb747e2..3d976e01f04bb722aa2d573ef3616173c5c70302 100644 (file)
--- a/README.md
+++ b/README.md
@@ -134,6 +134,8 @@ A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
 
 ```yaml
 language: rust
+rust:
+- nightly
 before_script:
 - rustup component add rustfmt-preview
 script: