Setup travis to do matrix builds with ruby for libimagruby

.travis.yml

@@ -1,14 +1,40 @@
 sudo: false
+os:
+  - linux
+
+dist:
+  - trusty
+
 language: rust
-rust:
-- 1.13.0
-- beta
-- stable
-cache: cargo
+
+matrix:
+  include:
+    - rust: 1.13.0
+      env: IMAG_RUBY_VERSION=2.3.3
+    - rust: beta
+      env: IMAG_RUBY_VERSION=2.3.3
+    - rust: stable
+      env: IMAG_RUBY_VERSION=2.3.3
+
+cache:
+  cargo: true
+  directories:
+    - $TRAVIS_BUILD_DIR/libimagruby/vendor/bundle
+
+before_install:
+- |
+  rvm install "$IMAG_RUBY_VERSION"
+  rvm use "$IMAG_RUBY_VERSION"
+  ruby --version
+  pushd libimagruby
+  bundle install --jobs=3 --retry=3 --path=$TRAVIS_BUILD_DIR/libimagruby/vendor/bundle
+  popd
+
 before_script:
 - |
   pip install 'travis-cargo<0.2' --user &&
   export PATH=$HOME/.local/bin:$PATH
+
 script:
 - |
   make all test
@@ -25,12 +51,14 @@ addons:
     - tree
     sources:
     - kalakris-cmake
+
 after_success:
 - |
   pushd .imag-documentation &&
   travis-cargo --only stable doc &&
   travis-cargo --only stable doc-upload
   popd
+
 notifications:
   email:
     on_success: never
@@ -39,7 +67,11 @@ notifications:
     - chat.freenode.net#imag
     template:
     - "%{repository_name} (%{branch} @ %{commit} by %{author}): %{result}"
+
 env:
   global:
-  - TRAVIS_CARGO_NIGHTLY_FEATURE=dev
-  - secure: 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
+    - THERMITE_DEBUG_FILENAME=/tmp/thermite-debug.log
+    - secure: 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
+  matrix:
+    - IMAG_RUBY_VERSION=2.3.3
+    - IMAG_RUBY_VERSION=2.4.0