Use describe on new feature tests

The `type: :feature` is automatically detected by RSpec because these
tests are inside the `spec/features` folder. Using `feature` re-adds a
`type: :feature` to these files, which will result in a conflict when we
upgrade to Rails 5.1's system tests.

Because of this change, we also need to change `background` to `before`
or else these tests will fail.

We're also adding a rubocop rule so we dont' accidentally add these
keywords again.

spec/features/legislation/resume_spec.rb

@@ -1,6 +1,6 @@
 require "rails_helper"
 
-feature "Legislation" do
+describe "Legislation" do
   context "process resume page" do
 
     scenario "resume tab not show" do