Travis: Add minimum support Rust version and 32-bit support

Author: chansuke

.travis.yml

@@ -10,6 +10,7 @@ rust:
   - nightly
   - beta
   - stable
+  - 1.13.0
 os:
   - linux
   - osx
@@ -27,7 +28,16 @@ script:
     done
   - ./test-scripts/check-copyright-comments.sh
 
+env:
+  - ARCH=x86_64
+  - ARCH=i686
+
+script:
+  - cd */
+  - curl -sSL https://raw.githubusercontent.com/carllerche/travis-rust-matrix/master/test | bash
+
 env:
   global:
     # Override the default `--features unstable` used for the nightly branch
     - TRAVIS_CARGO_NIGHTLY_FEATURE=""
+