Cast divmod quotient to int

[mrzasa]

Changes

Cast the quotient of divmod to integer.

It seems to be reasonable to make this change on the last step - just before returning to the caller, not inside BigDecimal_DoDivmod. BigDecimal_DoDivmod is widely used in other places of the gem and changing its inteface would be cumbersome and risky.

Rationale

Float and Integer return an Integer as the first result of #divmod.

 pry(main)> 10.0.divmod(3)
=> [3, 1.0]
 pry(main)> 10.divmod(3)
=> [3, 1]

Fixes #262
Blocked by #313