Fix disabling of array column type in AR adapter

Previously column types that matched `_array` were disabled as a Postgres specific workaround. ActiveRecord stopped using those column type names though.

Now a text array, for example, has column type of `text` and the `array` boolean attribute set to `true`. Instead of using the `DISABLED_COLUMN_MATCHERS`, we're now checking the `array` attribute.
Merge pull request #1960 from swalkinshaw/patch-1

Fix disabling of array column type in AR adapter