Add testing in stable/beta branches

.travis.yml

@@ -23,11 +23,16 @@ matrix:
     # Uniquely identifies the build that uploads to crates.io
     - env: CRATESIO=TRUE
       rust: nightly
-    - rust: nightly
-    # To build against specific Rust versions, include an item like the following:
-    # - rust: 1.30.0
+    - rust: 1.31.0
     - rust: nightly
       os: osx
+    - rust: stable
+      os: osx
+    - rust: beta
+      os: osx
+    - rust: nightly
+    - rust: stable
+    - rust: beta
 
 before_install:
   - set -e

appveyor.yml

@@ -11,6 +11,10 @@ environment:
     #   RUST_VERSION: nightly
     - TARGET: x86_64-pc-windows-msvc
       RUST_VERSION: nightly
+    - TARGET: x86_64-pc-windows-msvc
+      RUST_VERSION: stable
+    - TARGET: x86_64-pc-windows-msvc
+      RUST_VERSION: beta
 
 install:
   - ps: >-