add Storable a => Storable (Ratio a) and Storable a => Storable (Complex a) to base

[Herbert Valerio Riedel]

On 2014-11-03 at 18:57:27 +0100, John Lato wrote:
> Rather it makes me question whether `Ratio a` itself makes
> sense, and perhaps we should monomorphize it to Integers.  But that's a
> very different proposal.

IMHO, 'Ratio Natural' would be an example for something useful besides 'Ratio Integer'