Enables RSpec/ExampleWording and fixes all issues

Both avoiding 'should' and repiting 'it' on the tests description
improves reading them and also makes all descriptions consistent.

Read about cop at http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/ExampleWording

spec/controllers/management/sessions_controller_spec.rb

@@ -3,13 +3,13 @@ require 'rails_helper'
 describe Management::SessionsController do
 
   describe 'Sign in' do
-    it "should deny access if wrong manager credentials" do
+    it "denies access if wrong manager credentials" do
       allow_any_instance_of(ManagerAuthenticator).to receive(:auth).and_return(false)
       expect { get :create, login: "nonexistent", clave_usuario: "wrong"}.to raise_error CanCan::AccessDenied
       expect(session[:manager]).to be_nil
     end
 
-    it "should redirect to management root path if authorized manager with right credentials" do
+    it "redirects to management root path if authorized manager with right credentials" do
       manager = {login: "JJB033", user_key: "31415926", date: "20151031135905"}
       allow_any_instance_of(ManagerAuthenticator).to receive(:auth).and_return(manager)
 
@@ -18,7 +18,7 @@ describe Management::SessionsController do
       expect(session[:manager][:login]).to eq "JJB033"
     end
 
-    it "should redirect to management root path if user is admin" do
+    it "redirects to management root path if user is admin" do
       user = create(:administrator).user
       sign_in user
       get :create
@@ -26,7 +26,7 @@ describe Management::SessionsController do
       expect(session[:manager][:login]).to eq "admin_user_#{user.id}"
     end
 
-    it "should redirect to management root path if user is manager" do
+    it "redirects to management root path if user is manager" do
       user = create(:manager).user
       sign_in user
       get :create
@@ -34,7 +34,7 @@ describe Management::SessionsController do
       expect(session[:manager][:login]).to eq "manager_user_#{user.id}"
     end
 
-    it "should deny access if user is not admin or manager" do
+    it "denies access if user is not admin or manager" do
       sign_in create(:user)
       expect { get :create}.to raise_error CanCan::AccessDenied
       expect(session[:manager]).to be_nil
@@ -42,7 +42,7 @@ describe Management::SessionsController do
   end
 
   describe 'Sign out' do
-    it "should destroy the session data and redirect" do
+    it "destroys the session data and redirect" do
       session[:manager] = {user_key: "31415926", date: "20151031135905", login: "JJB033"}
       session[:document_type] = "1"
       session[:document_number] = "12345678Z"