Disable testtask warnings

They were enabled by default in rake 11, but they generate far too much
output for travis to handle.

Author: glebm

Rakefile

@@ -5,7 +5,8 @@ require 'rake/testtask'
 Rake::TestTask.new do |t|
   t.libs << 'test'
   t.test_files = FileList['test/**/*_test.rb']
-  t.verbose = true
+  t.verbose = false
+  t.warning = false
 end
 
 desc 'Test all Gemfiles from test/*.gemfile'