Bump minimum Rust version to 1.13

See rust-lang/libc#972

Author: lambda-fairy

.travis.yml

@@ -4,11 +4,11 @@ os:
   - osx
 rust:
   - stable
-  - 1.8.0
+  - 1.13.0
 matrix:
   exclude:
     # https://github.com/rust-lang/rust/issues/34674
     - os: osx
-      rust: 1.8.0
+      rust: 1.13.0
 script:
   - cargo test

README.md

@@ -1,6 +1,6 @@
 # errno [![Build status](https://img.shields.io/travis/lfairy/rust-errno.svg)](http://travis-ci.org/lfairy/rust-errno) [![Build status](https://ci.appveyor.com/api/projects/status/0fgngg808u7xwto8?svg=true)](https://ci.appveyor.com/project/lfairy/rust-errno) [![Cargo](https://img.shields.io/crates/v/errno.svg)](https://crates.io/crates/errno)
 
-Cross-platform interface to the [`errno`][errno] variable. Works on Rust 1.8 or newer.
+Cross-platform interface to the [`errno`][errno] variable. Works on Rust 1.13 or newer.
 
 Documentation is available at <https://docs.rs/errno>.