Bump rustc to 1.12.0

.travis.yml

@@ -11,7 +11,7 @@ matrix:
       env: TARGET=x86_64-apple-darwin
       cache: cargo
     - os: linux
-      rust: 1.11.0
+      rust: 1.12.0
       env: TARGET=x86_64-unknown-linux-gnu
       cache: cargo
     - os: linux

CHANGELOG.md

@@ -1,7 +1,7 @@
 **Version 0.13.0**
  - Fix bug in certain PNG headers when reducing color type ([#52](https://github.com/shssoichiro/oxipng/issues/52))
  - [SEMVER_MAJOR] Reduction functions now take `&mut PngData` and return a `bool` indicating whether the image was reduced
- - Bump minimum required rust version to 1.11.0
+ - Bump minimum required rust version to 1.12.0
 
 **Version 0.12.0**
  - Performance optimizations

README.md

@@ -30,7 +30,7 @@ cp target/release/oxipng /usr/local/bin
 Please note that zlib is a required build dependency. Oxipng should work with any 1.x version of zlib,
 but you are advised to use the latest version (currently 1.2.8) for security and bug fixes.
 
-The current minimum supported Rust version is **1.11.0**. Oxipng may compile on earlier versions of Rust,
+The current minimum supported Rust version is **1.12.0**. Oxipng may compile on earlier versions of Rust,
 but there is no guarantee.
 
 Oxipng follows Semantic Versioning.