chore: Update stable Rust

Author: epage

.travis.yml

@@ -8,13 +8,13 @@ rust:
 matrix:
   include:
   - env: RUSTFMT
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
+    rust: 1.27.0  # `stable`: Locking down for consistent behavior
     install:
       - rustup component add rustfmt-preview
     script:
       - cargo fmt -- --write-mode=diff
   - env: RUSTFLAGS="-D warnings"
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
+    rust: 1.27.0  # `stable`: Locking down for consistent behavior
     install:
     script:
     - cargo check --tests --all-features