This is recommended by the Rails 4.0 upgrade guide:
> The caching method changed between Rails 3.x and 4.0. You should change the cache namespace and roll out with a cold cache.
I noticed too that old cache entries with old character encodings were a real problem, so yeah making sure we're working with a cold cache is smart!!
NOTE: This doesn't boot yet! There's something changed in the `devise` API that we'll need to fix!
```
/vagrant/config/initializers/devise.rb:46:in `block in <top (required)>': undefined method `encryptor=' for Devise:Module (NoMethodError)
```
But yeah, we navigated the gem upgrades, and also I ran `rake rails:update` and hand-processed the suggestions it had for our config files.
