Use activerecord reorder method instead of order

[KRaikk]

Order queries with ActiveRecord's reorder method to force ordering by given array as collection can prepend an order:

class User < ActiveRecord::Base
...
scope :latest, -> { order created_at: :desc }

names = %w(Pearl John)

User.latest.pluck(:name)
# => ['John', 'Kathenrie', 'Pearl']

User.latest.with_order(:name, names).pluck(:name)
# With current code 'latest' scope's order will execute first:
# => ['John', 'Kathenrie', 'Pearl']

# With this pull request, reorder will force ordering by given 'names' array:
# => ['Pearl', 'John', 'Kathenrie']

[khiav223577]

Thanks for you PR.

It would be better to make this feature optional since these changes will change original behavior. There are also some cases that may not want to replace existing orders. For example, I want to order the players by their score and if the score is the same, order by given school names.

players.order(:score).with_order(:school_name, school_names)

It would also be nice to have some test cases for the new feature :).

[khiav223577]

The changes made to README.md is not suitable for this PR.