[CI] Update travis.yml download url and matrix (elastic#801)

* [CI] Update url to download elasticsearch in travis yml

* [CI] Include ruby 2.5.1 in travis matrix

* [CI] Update test to account for #to_ary called on objects recursively via #flatten in ruby < 2.3

* [CI] Further updates to travis matrix for latest versions in each series

* [CI] Remove extra line for debugging

Author: estolfo

.travis.yml

@@ -20,24 +20,28 @@ branches:
 
 matrix:
   include:
-    - rvm: 2.2.6
+    - rvm: 2.2.10
       jdk: oraclejdk8
       env: TEST_SUITE=unit
 
-    - rvm: 2.3.3
+    - rvm: 2.3.7
+      jdk: oraclejdk8
+      env: TEST_SUITE=unit
+
+    - rvm: 2.5.1
       jdk: oraclejdk8
       env: TEST_SUITE=unit
 
     - rvm: 2.3.3
       jdk: oraclejdk8
-      env: TEST_SUITE=integration QUIET=y SERVER=start TEST_CLUSTER_LOGS=/tmp/log TEST_CLUSTER_COMMAND=/tmp/elasticsearch-6.0.0-alpha1-SNAPSHOT/bin/elasticsearch
+      env: TEST_SUITE=integration QUIET=y SERVER=start TEST_CLUSTER_LOGS=/tmp/log TEST_CLUSTER_COMMAND=/tmp/elasticsearch-6.3.0/bin/elasticsearch
 
 before_install:
   - gem update --system --no-rdoc --no-ri
   - gem --version
   - gem install bundler -v 1.14.3 --no-rdoc --no-ri
   - bundle version
-  - curl -sS https://snapshots.elastic.co/downloads/elasticsearch/elasticsearch-6.0.0-alpha1-SNAPSHOT.tar.gz | tar xz -C /tmp
+  - curl -sS https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.3.0.tar.gz | tar xz -C /tmp
 
 install:
   - bundle install

elasticsearch-model/test/unit/multimodel_test.rb

@@ -4,8 +4,8 @@ class Elasticsearch::Model::MultimodelTest < Test::Unit::TestCase
 
   context "Multimodel class" do
     setup do
-      title  = stub('Foo', index_name: 'foo_index', document_type: 'foo')
-      series = stub('Bar', index_name: 'bar_index', document_type: 'bar')
+      title  = stub('Foo', index_name: 'foo_index', document_type: 'foo', to_ary: nil)
+      series = stub('Bar', index_name: 'bar_index', document_type: 'bar', to_ary: nil)
       @multimodel = Elasticsearch::Model::Multimodel.new(title, series)
     end