v4.0.0

4.0.0 chosen arbitrarily since there was only one tag/release here previously

recent changes include:

• landing page druids configured per environment so -stage and -dev don't give 404 error
• upgrade to Rails 5
• use okcomputer at /status to replace is_it_working
  • is_it_working updates
• use honeybadger instead of squash
• reduce log output, partially by using lograge
• capistrano deployment updates
  ...