Add config/tokens.yml template
Remove secret_token.rb
Load secret_key_base from tokens.yml, fallback to config.secret_key_base
Replace config.secret_key_base with secrets.secret_key_base in test
Add test for custom tokens stored in config/tokens.yml
docs guidelines: recommends wording in a way that avoids "you"s and "your"s
Remove delegation test.

This test was removed, since Relation will not delegate class
methods to Array.
Add changelog
Use a whitelist to delegate methods to array
Rename tokens.yml to secrets.yml
Use `public_send` instead of just use `send`.
pull a nil check up one frame
extract methods out of the cache update method
extract a method for updating without a record object
remove duplicate code
extract cache counter logic to one method
Merge pull request #12590 from laurocaetano/whitelist-to-delegate-array-methods

Create a whitelist of methods to be delegated to Array.
fix grammatical error
Merge pull request #13302 from afshinator/master

fix grammatical error
Perf: save ~9% of object allocations on heavy requests.

The per-thread registry is keyed on the class name, and each request for
the class name returns a new string. This is in the hot path for a lot
of Active Record behavior, so we easily accumulate thousands of repeated
strings.

To fix, we simply cache the key when the class is first extended with
the module.

TODO: Eliminate this module. The per-thread instance concept is common,
but this technique confuses and obfuscates.