Implements #150

Adds an entry inside moderation section that allows moderators to check
pending tasks and mark them as solved.

spec/models/abilities/moderator_spec.rb

@@ -21,6 +21,7 @@ describe Abilities::Moderator do
   let(:hidden_debate) { create(:debate, :hidden) }
   let(:hidden_comment) { create(:comment, :hidden) }
   let(:hidden_proposal) { create(:proposal, :hidden) }
+  let(:administrator_task) { create(:administrator_task) }
 
   it { should be_able_to(:index, Debate) }
   it { should be_able_to(:show, debate) }
@@ -31,6 +32,9 @@ describe Abilities::Moderator do
 
   it { should be_able_to(:read, Organization) }
 
+  it { is_expected.to be_able_to :manage, AdministratorTask }
+  it { is_expected.to be_able_to :manage, administrator_task }
+
   describe "organizations" do
     let(:pending_organization)  { create(:organization) }
     let(:rejected_organization) { create(:organization, :rejected) }