Enable multiple Bazel versions in Travis (#96)

.travis.yml

@@ -11,14 +11,34 @@ addons:
       - zip
       - unzip
       - zlib1g-dev
+
 jdk:
   - oraclejdk8
 
+env:
+  - V=HEAD URL=http://ci.bazel.io/job/Bazel/JAVA_VERSION=1.8,PLATFORM_NAME=linux-x86_64/lastSuccessfulBuild/artifact/output/ci/bazel--installer.sh FLAGS='--worker_verbose --strategy=Javac=worker --strategy=JsChecker=worker'
+  - V=0.3.0 URL=http://bazel-mirror.storage.googleapis.com/github.com/bazelbuild/bazel/releases/download/0.3.0/bazel-0.3.0-installer-linux-x86_64.sh FLAGS=''
+  - V=0.2.2b URL=http://bazel-mirror.storage.googleapis.com/github.com/bazelbuild/bazel/releases/download/0.2.2b/bazel-0.2.2b-installer-linux-x86_64.sh FLAGS=''
+
 before_install:
-  - wget 'https://github.com/bazelbuild/bazel/releases/download/0.2.2b/bazel-0.2.2b-installer-linux-x86_64.sh'
-  - '[[ "$(sha256sum <bazel-0.2.2b-installer-linux-x86_64.sh)" == "4b45fbafe3376e3a6016641f8d2169a581272d93d81b736f33daeb21a4105df0  -" ]]'
-  - chmod +x bazel-0.2.2b-installer-linux-x86_64.sh
-  - ./bazel-0.2.2b-installer-linux-x86_64.sh --user
+  - wget -O install.sh $URL
+  - chmod +x install.sh
+  - ./install.sh --user
+  - rm -f install.sh
 
 script:
-  - bazel --batch --host_jvm_args=-Xmx1000m --host_jvm_args=-Xms1000m test closure/... --verbose_failures --test_output=errors --test_strategy=standalone --spawn_strategy=standalone --genrule_strategy=standalone --local_resources=1000,1,1.0
+  - |
+    bazel \
+      --output_base=$HOME/.cache/bazel \
+      --batch \
+      --host_jvm_args=-Xmx1000m \
+      --host_jvm_args=-Xms1000m \
+      test \
+      closure/... \
+      --verbose_failures \
+      --test_output=errors \
+      --test_strategy=standalone \
+      --spawn_strategy=standalone \
+      --genrule_strategy=standalone \
+      --local_resources=1000,1,1.0 \
+      $FLAGS