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/models/legislation/proposal_spec.rb

@@ -3,26 +3,26 @@ require 'rails_helper'
 describe Legislation::Proposal do
   let(:proposal) { build(:legislation_proposal) }
 
-  it "should be valid" do
+  it "is valid" do
     expect(proposal).to be_valid
   end
 
-  it "should not be valid without a process" do
+  it "is not valid without a process" do
     proposal.process = nil
     expect(proposal).to_not be_valid
   end
 
-  it "should not be valid without an author" do
+  it "is not valid without an author" do
     proposal.author = nil
     expect(proposal).to_not be_valid
   end
 
-  it "should not be valid without a title" do
+  it "is not valid without a title" do
     proposal.title = nil
     expect(proposal).to_not be_valid
   end
 
-  it "should not be valid without a summary" do
+  it "is not valid without a summary" do
     proposal.summary = nil
     expect(proposal).to_not be_valid
   end