Bump minimum supported rustc to 1.27

.travis.yml

@@ -8,7 +8,7 @@ matrix:
     - os: osx
 
     # rustc version compat
-    - rust: 1.22.0 # oldest supported version, keep in sync with README.md
+    - rust: 1.27.0 # oldest supported version, keep in sync with README.md
     - rust: beta
     - rust: nightly
 

README.md

@@ -30,7 +30,7 @@ Table of Contents (ToC)
 Build Requirements
 ------------------
 
-Sccache is a [Rust](https://www.rust-lang.org/) program. Building it requires `cargo` (and thus `rustc`). sccache currently requires **Rust 1.22**.
+Sccache is a [Rust](https://www.rust-lang.org/) program. Building it requires `cargo` (and thus `rustc`). sccache currently requires **Rust 1.27**.
 
 We recommend you install Rust via [Rustup](https://rustup.rs/). The generated binaries can be built so that they are very [portable](#building-portable-binaries). By default `sccache` supports a local disk cache. To build `sccache` with support for `S3` and/or `Redis` cache backends, add `--features=all` or select a specific feature by passing `s3`, `gcs`, and/or `redis`. Refer the [Cargo Documentation](http://doc.crates.io/manifest.html#the-features-section) for details.
 

appveyor.yml

@@ -35,7 +35,7 @@ for:
         target: x86_64-pc-windows-msvc
       - channel: nightly
         target: x86_64-pc-windows-msvc
-      - channel: 1.22.0 # Oldest supported version. Keep in sync with README.md.
+      - channel: 1.27.0 # Oldest supported version. Keep in sync with README.md.
         target: x86_64-pc-windows-msvc
         # Build a release build on master to make sure it builds.
       - channel: stable