Refactoring: Move 'vote' action to Votes Controllers

As far as possible I think the code is clearer if we use CRUD actions
rather than custom actions. This will make it easier to add the action
to remove votes in the next commit.

Note that we are adding this line as we need to validate it that a vote
can be created on a debate by the current user:

```authorize! :create, Vote.new(voter: current_user, votable: @debate)```

We have done it this way and not with the following code as you might
expect, as this way two votes are created instead of one.

```load_and_authorize_resource through: :debate, through_association: :votes_for```

This line tries to load the resource @debate and through the association
"votes_for" it tries to create a new vote associated to that debate.
Therefore a vote is created when trying to authorise the resource and
then another one in the create action, when calling @debate.vote_by (which
is called by @debate.register_vote).

spec/models/abilities/common_spec.rb

@@ -7,6 +7,7 @@ describe Abilities::Common do
   let(:geozone)     { create(:geozone)  }
 
   let(:user) { create(:user, geozone: geozone) }
+  let(:another_user) { create(:user) }
 
   let(:debate)       { create(:debate)   }
   let(:comment)      { create(:comment)  }
@@ -15,6 +16,7 @@ describe Abilities::Common do
   let(:own_comment)  { create(:comment,  author: user) }
   let(:own_proposal) { create(:proposal, author: user) }
   let(:own_legislation_proposal) { create(:legislation_proposal, author: user) }
+  let(:legislation_proposal) { create(:legislation_proposal) }
 
   let(:accepting_budget) { create(:budget, :accepting) }
   let(:reviewing_budget) { create(:budget, :reviewing) }
@@ -73,7 +75,8 @@ describe Abilities::Common do
 
   it { should be_able_to(:index, Debate) }
   it { should be_able_to(:show, debate)  }
-  it { should be_able_to(:vote, debate)  }
+  it { should be_able_to(:create, user.votes.build(votable: debate)) }
+  it { should_not be_able_to(:create, another_user.votes.build(votable: debate)) }
 
   it { should be_able_to(:show, user) }
   it { should be_able_to(:edit, user) }
@@ -137,20 +140,16 @@ describe Abilities::Common do
   end
 
   describe "follows" do
-    let(:other_user) { create(:user) }
-
     it { should be_able_to(:create, build(:follow, :followed_proposal, user: user)) }
-    it { should_not be_able_to(:create, build(:follow, :followed_proposal, user: other_user)) }
+    it { should_not be_able_to(:create, build(:follow, :followed_proposal, user: another_user)) }
 
     it { should be_able_to(:destroy, create(:follow, :followed_proposal, user: user)) }
-    it { should_not be_able_to(:destroy, create(:follow, :followed_proposal, user: other_user)) }
+    it { should_not be_able_to(:destroy, create(:follow, :followed_proposal, user: another_user)) }
   end
 
   describe "other users" do
-    let(:other_user) { create(:user) }
-
-    it { should     be_able_to(:show, other_user) }
-    it { should_not be_able_to(:edit, other_user) }
+    it { should     be_able_to(:show, another_user) }
+    it { should_not be_able_to(:edit, another_user) }
   end
 
   describe "editing debates" do
@@ -182,6 +181,18 @@ describe Abilities::Common do
   it { should_not be_able_to(:edit, own_legislation_proposal) }
   it { should_not be_able_to(:update, own_legislation_proposal) }
 
+  describe "vote legislation proposal" do
+    context "when user is not level_two_or_three_verified" do
+      it { should_not be_able_to(:create, user.votes.build(votable: legislation_proposal)) }
+    end
+
+    context "when user is level_two_or_three_verified" do
+      before { user.update(level_two_verified_at: Date.current) }
+      it { should be_able_to(:create, user.votes.build(votable: legislation_proposal)) }
+      it { should_not be_able_to(:create, another_user.votes.build(votable: legislation_proposal)) }
+    end
+  end
+
   describe "proposals dashboard" do
     it { should be_able_to(:dashboard, own_proposal) }
     it { should_not be_able_to(:dashboard, proposal) }