sferik/rails_admin — pull request #1927 by yangchenyun (2014-03-07 10:06:06+00:00)
Title: added includes method to enable explicit join with associated tables

added `includes(*join_tables)` to include the associated tables explicitly because `references` doesn't know whether the associated tables are being loaded.

otherwise, a ERROR will be thrown for undefined tables. For example
```
class Person
has_many :phone_numbers

rails_admin do
configure :phone_numbers, :has_many_association
list do
field :phone_numbers do
searchable ['phone_numbers.number']
end
end
end
end
```
will throw an error
```
`SELECT "people".* FROM "people" WHERE ((LOWER(phone_numbers.location) ILIKE '%13%')) ORDER BY people.id desc LIMIT 20 OFFSET 0`
```