update travis, rakefile, and protoc

- add ruby 2.6 to travis, remove EOL-ed rubies
- the newer versions of protoc have a --ruby_out that takes precedence,
alias the ruby plugin so it works with new versions of protoc
- use binary protoc version 3.8.0

.travis.yml

@@ -7,30 +7,20 @@ before_install:
   - sudo make install
   # Retrun to project directory
   - cd ..
-  - sudo -E ./install-protobuf.sh
+  - curl -SsfL -O https://github.com/protocolbuffers/protobuf/releases/download/v3.8.0/protoc-3.8.0-linux-x86_64.zip
+  - sudo -E unzip -d /usr protoc-3.8.0-linux-x86_64.zip
   - java -Xmx1g -version
   - javac -J-Xmx1g -version
   - export JRUBY_OPTS=-J-Xmx1g
   - gem update bundler
 language: ruby
 rvm:
-  - 1.9.3
-  - 2.0.0
-  - 2.1
-  - 2.2
   - 2.3
   - 2.4
   - 2.5
+  - 2.6
   - jruby-9.1.17.0
-  - jruby-9.2.5.0
-  - rbx-2
-env:
-  - PROTOBUF_VERSION=2.6.1
-  - PROTOBUF_VERSION=3.0.0-alpha-2
-matrix:
-  allow_failures:
-    - rvm: rbx-2
-    - env: PROTOBUF_VERSION=3.0.0-alpha-2
+  - jruby-9.2.7.0
 notifications:
   webhooks:
     urls:

Rakefile

@@ -18,11 +18,11 @@ task :default => ['compile:spec', 'compile:rpc', :spec, :rubocop]
 desc 'Run specs'
 namespace :compile do
 
-  desc 'Compile spec protos in spec/supprt/ directory'
+  desc 'Compile spec protos in spec/support/ directory'
   task :spec do
     proto_path = ::File.expand_path('../spec/support/', __FILE__)
     proto_files = Dir[File.join(proto_path, '**', '*.proto')]
-    cmd = %(protoc --plugin=./bin/protoc-gen-ruby --ruby_out=#{proto_path} -I #{proto_path} #{proto_files.join(' ')})
+    cmd = %(protoc --plugin=protoc-gen-ruby-protobuf=./bin/protoc-gen-ruby --ruby-protobuf_out=#{proto_path} -I #{proto_path} #{proto_files.join(' ')})
 
     puts cmd
     system(cmd)
@@ -35,7 +35,7 @@ namespace :compile do
     output_dir = ::File.expand_path('../tmp/rpc', __FILE__)
     ::FileUtils.mkdir_p(output_dir)
 
-    cmd = %(protoc --plugin=./bin/protoc-gen-ruby --ruby_out=#{output_dir} -I #{proto_path} #{proto_files.join(' ')})
+    cmd = %(protoc --plugin=protoc-gen-ruby-protobuf=./bin/protoc-gen-ruby --ruby-protobuf_out=#{output_dir} -I #{proto_path} #{proto_files.join(' ')})
 
     puts cmd
     system(cmd)