Require a little more clarity on the Upgrade ReadMe

[AaronRustad]

I wonder if you can provide a little more clarity on the steps to upgrade to 0.4.0 README. In a typical production environment, are you suggesting at each numbered step is followed by a deploy to production?

For example:

1. Upgrade gem to 0.4.0, adjust key_hash_stage, deploy to production
2. Run AddKeyHashAndByteSizeToSolidCacheEntries migration, deploy to production
3. Update config, deploy to production
   ...

Or can all the steps be followed and executed in development, committed and deployed in their entirety in production?

I'm happy to update the Readme once I understand the correct approach.
Thanks!