Enable RSpec/LetBeforeExamples cop & fix issues

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

.rubocop.yml

@@ -114,4 +114,7 @@ RSpec/IteratedExpectation:
   Enabled: true
 
 RSpec/LeadingSubject:
+  Enabled: true
+
+RSpec/LetBeforeExamples:
   Enabled: true

spec/features/budgets/investments_spec.rb

@@ -3,9 +3,6 @@ require 'sessions_helper'
 
 feature 'Budget Investments' do
 
-  context "Concerns" do
-    it_behaves_like 'notifiable in-app', Budget::Investment
-  end
 
   let(:author)  { create(:user, :level_two, username: 'Isabel') }
   let(:budget)  { create(:budget, name: "Big Budget") }
@@ -21,6 +18,10 @@ feature 'Budget Investments' do
     Setting['feature.allow_images'] = nil
   end
 
+  context "Concerns" do
+    it_behaves_like 'notifiable in-app', Budget::Investment
+  end
+
   scenario 'Index' do
     investments = [create(:budget_investment, heading: heading),
                    create(:budget_investment, heading: heading),

spec/features/comments/legislation_questions_spec.rb

@@ -3,14 +3,14 @@ include ActionView::Helpers::DateHelper
 
 feature 'Commenting legislation questions' do
 
-  context "Concerns" do
-    it_behaves_like 'notifiable in-app', Legislation::Question
-  end
-
   let(:user) { create :user, :level_two }
   let(:process) { create :legislation_process, :in_debate_phase }
   let(:legislation_question) { create :legislation_question, process: process }
 
+  context "Concerns" do
+    it_behaves_like 'notifiable in-app', Legislation::Question
+  end
+
   scenario 'Index' do
     3.times { create(:comment, commentable: legislation_question) }
 

spec/models/budget/group_spec.rb

@@ -2,10 +2,10 @@ require 'rails_helper'
 
 describe Budget::Group do
 
-  it_behaves_like "sluggable"
-
   let(:budget) { create(:budget) }
 
+  it_behaves_like "sluggable"
+
   describe "name" do
     before do
       create(:budget_group, budget: budget, name: 'object name')

spec/models/budget/heading_spec.rb

@@ -2,11 +2,11 @@ require 'rails_helper'
 
 describe Budget::Heading do
 
-  it_behaves_like "sluggable"
-
   let(:budget) { create(:budget) }
   let(:group) { create(:budget_group, budget: budget) }
 
+  it_behaves_like "sluggable"
+
   describe "name" do
     before do
       create(:budget_heading, group: group, name: 'object name')