Bump min. required Rust version to 1.40

.travis.yml

@@ -32,15 +32,15 @@ matrix:
 
     # Minimum Rust supported channel.
     - os: linux
-      rust: 1.37.0
+      rust: 1.40.0
       env: TARGET=x86_64-unknown-linux-gnu
     - os: linux
-      rust: 1.37.0
+      rust: 1.40.0
       env:
         - TARGET=x86_64-unknown-linux-musl
         - CC_x86_64_unknown_linux_musl=/usr/bin/musl-gcc
     - os: osx
-      rust: 1.37.0
+      rust: 1.40.0
       env: TARGET=x86_64-apple-darwin
 
     # Disable nightly for now

README.md

@@ -348,7 +348,7 @@ binaries are also available: look for archives with `musl` in the file name.
 
 ### From source
 
-If you want to build `bat` from source, you need Rust 1.37 or
+If you want to build `bat` from source, you need Rust 1.40 or
 higher. You can then use `cargo` to build everything:
 
 ```bash