Use describe on 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.

spec/shared/features/admin_milestoneable.rb

@@ -1,7 +1,7 @@
 shared_examples "admin_milestoneable" do |factory_name, path_name|
   it_behaves_like "admin_progressable", factory_name, path_name
 
-  feature "Admin milestones" do
+  describe "Admin milestones" do
     let!(:milestoneable) { create(factory_name) }
     let(:path) { send(path_name, *resource_hierarchy_for(milestoneable)) }
 

spec/shared/features/admin_progressable.rb

@@ -1,7 +1,7 @@
 shared_examples "admin_progressable" do |factory_name, path_name|
   let!(:progressable) { create(factory_name) }
 
-  feature "Manage progress bars" do
+  describe "Manage progress bars" do
     let(:progressable_path) { send(path_name, *resource_hierarchy_for(progressable)) }
 
     let(:path) do

spec/shared/features/imageable_destroy.rb

@@ -22,7 +22,7 @@ shared_examples "imageable destroy" do |imageable_factory_name,
 
   context "Destroy" do
 
-    background do
+    before do
       create(:image, imageable: imageable, user: imageable.author)
     end
 

spec/shared/features/milestoneable.rb

@@ -3,7 +3,7 @@ shared_examples "milestoneable" do |factory_name, path_name|
 
   let!(:milestoneable) { create(factory_name) }
 
-  feature "Show milestones" do
+  describe "Show milestones" do
     let(:path) { send(path_name, *resource_hierarchy_for(milestoneable)) }
 
     scenario "Show milestones", :js do

spec/shared/features/progressable.rb

@@ -1,5 +1,5 @@
 shared_examples "progressable" do |factory_name, path_name|
-  feature "Progress bars", :js do
+  describe "Progress bars", :js do
     let!(:progressable) { create(factory_name) }
     let(:path) { send(path_name, *resource_hierarchy_for(progressable)) }