Render a list of all Note records notes#index

This commit addresses the previous error:

Failure:
  UserDiscoversANoteTest#test_from_the_root [/Users/seanpdoyle/src/prix-fixe/test/system/user_discovers_a_note_test.rb:9]:
  expected to find text "Hello, World" in "Share a Note"

By iterating over the collection returned by a Note.all invocation to our notes#index template, our application renders the #content into our response’ HTML.

This “solution” addresses the immediate failure message in a minimal and simple way.

When our system test is executed, it passes.