Set {source,target}_version to work with the current version of javac on macOS

.travis.yml

@@ -1,5 +1,4 @@
 sudo: false
-dist: trusty
 language: ruby
 
 rvm:
@@ -13,11 +12,13 @@ rvm:
   - 2.6.6
   - 2.7.1
   - jruby-19mode
-  - jruby-head
+  - jruby-9.0
+  - jruby-9.1
+  - jruby-9.2
 
 before_install:
-  - '[[ "$(ruby --version)" == *"1.9.3"* ]] && gem update --system 2.4.8 || true'
+  - '[[ "$(ruby --version)" != *"1.9.3"* ]] || gem update --system 2.4.8'
 
 script:
   - bundle exec rake compile
-  - bundle exec rspec -c spec
+  - bundle exec rspec

Rakefile

@@ -9,6 +9,8 @@ if RUBY_PLATFORM =~ /java/
   require 'rake/javaextensiontask'
   Rake::JavaExtensionTask.new('websocket-driver', spec) do |ext|
     ext.name = 'websocket_mask'
+    ext.source_version = '8'
+    ext.target_version = '8'
   end
 else
   require 'rake/extensiontask'