Run Go1.9 and 386 on Travis (#1475)

Author: dfawley

.travis.yml

@@ -4,12 +4,18 @@ go:
   - 1.6.x
   - 1.7.x
   - 1.8.x
+  - 1.9.x
+
+matrix:
+  include:
+  - go: 1.9.x
+    env: ARCH=386
 
 go_import_path: google.golang.org/grpc
 
 before_install:
-  - if [[ "$TRAVIS_GO_VERSION" = 1.8* ]]; then ./vet.sh -install || exit 1; fi
+  - if [[ "$TRAVIS_GO_VERSION" = 1.9* && "$ARCH" != "386" ]]; then ./vet.sh -install || exit 1; fi
 
 script:
-  - if [[ "$TRAVIS_GO_VERSION" = 1.8* ]]; then ./vet.sh || exit 1; fi
+  - if [[ "$TRAVIS_GO_VERSION" = 1.9* && "$ARCH" != "386" ]]; then ./vet.sh || exit 1; fi
   - make test testrace