Changed ActiveRecord::Relation#update behavior so that if only one attributes hash is passed, it will apply it to all ids.

- Right now, when you want to update multiple records with
  ActiveRecord::Relation#update with same values, you have to pass the values
  as array of hashes even if they are same
- This commit checks if the attributes is array of hashes or a single
  hash.
- If it's single hash, it updates all records from ids array
  with single hash.
- If it's array of hashes, it maps one id to one hash as the previous behavior.