Add Ruby 2.5 support (#648)

* Fix os version detection not to include newline
* Add ruby 2.4 and 2.5 to CI

spec/google/apis/core/service_spec.rb

@@ -36,6 +36,11 @@ RSpec.describe Google::Apis::Core::BaseService do
     expect(agent).to match /^test\/1.0/
   end
 
+  it 'should include os version in user agent' do
+    agent = service.send(:user_agent)
+    expect(agent).to match /#{Google::Apis::OS_VERSION}/
+  end
+
   it 'should inherit authorization' do
     Google::Apis::RequestOptions.default.authorization = 'a token'
     expect(service.authorization).to eql 'a token'

spec/google/apis/versions_spec.rb

@@ -0,0 +1,25 @@
+# Copyright 2015 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require 'spec_helper'
+require 'google/apis/version'
+
+RSpec.describe Google::Apis::VERSION do
+  it { is_expected.to be_a(String) }
+
+  describe Google::Apis::OS_VERSION do
+    it { is_expected.to be_a(String) }
+    it { is_expected.not_to match /\n/ }
+  end
+end