Task.clear does not remove parameters

[jessebs]

Task.clear does not remove the handling of parameters. This can easily be seen by the following example:

desc 'Original Test Task'
task :test, [:param] do; end

Rake::Task[:test].clear
desc 'Replaced Test Task'
task :test do; end

rake -T yields

rake test[param] # Replaced Test Task

Adding the following after the call to clear corrects it, so clear just needs to remove the params

Rake::Task[:test].instance_variable_set(:@arg_names, nil)

[hsbt]

Fixed at #157