Make assert_sql output easier to debug the problem

This is a small improvement to assert_sql, making the it's output easier to debug the problem.

Fox example for this failing test:

  def test_merged_scoped_find
    poor_jamis = developers(:poor_jamis)
    Developer.with_scope(:find => { :conditions => "salary < 100000" }) do
      Developer.with_scope(:find => { :offset => 1, :order => 'id asc' }) do
        assert_sql /ORDER BY id asc  / do
          assert_equal(poor_jamis, Developer.find(:first, :order => 'id asc'))
        end
      end
    end
  end

Instead of the current output:

Query pattern(s) /ORDER BY id asc  / not found.

You'll get something like this:

Query pattern(s) /ORDER BY id asc  / not found in SELECT * FROM `developers` WHERE (salary < 100000)  ORDER BY id asc LIMIT 1, 1.

Showing the executed queries and making easier to figure put why it isn't the expected result.