(QA-2941) re-enable rake 12

* acceptance previously showed a bug we had against rake 12
* really rake 12 just clarified how to use arguments to tasks so they
aren't confused with hashes: ruby/rake#171

rototiller.gemspec

@@ -15,7 +15,5 @@ Gem::Specification.new do |s|
                         'README.md', 'lib/**/*', 'docs/**/*']
   s.required_ruby_version = '>= 1.9.3'
 
-  # RAKE_VER=0.9, 10.0, 11.0
-  #   don't use 11.0.0, which probably installs 11.0.1 which has issues
-  s.add_runtime_dependency 'rake', '< 12.0.0'
+  s.add_runtime_dependency 'rake'
 end