Calling find() on an association with an inverse will now check to see
if the association already holds that record in memory before checking
the database for the specified ids.
Merge pull request #9529 from wangjohn/find_on_inverse_of_bugfix_9470

Find() on an association with an inverse will now scan existing in-memory records
Fix guides error on error class name

The error that's raised in case the required key is missing it's actually `ActionController::ParameterMissing` not `ActionController::MissingParameter`. It's important to fix so that people reading the guides knows what error to rescue from when needed.
Merge pull request #9816 from sebasoga/strong_parameters_guide_fix

Fix guides error on error class name