Revert "Split arel_table into method to get a relation and another to memoize the default relation."

This reverts commit bd517908.

Ruby 1.9.2: disallow explicit coercion via method_missing. Only give friendly nil errors for Array and Active Record methods.

Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

[#3451 state:committed]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

This reverts commit d8fd0499.

This reverts commit 1fcf32f8.

This reverts commit 90be8036.

Use an env var to expand the CI bundle. Using bundler's 'only' includes this stuff for everybody, oops.