Instances for `Fixed`

[lehins]

One more type from base that is missing some instances.

I think I can see a lawful implementation for HasResolution e => UniformRange (Fixed e) instance. Also considering that we already have instance Random Integer we can definitely add instance HasResolution e => Random (Fixed e)

[Shimuuar]

For a change I think UniformRange is perfectly reasonable instance. Only question is what should random return? I think it should follow Dounle/Float/proposed instance for Rationals and return numbers in [0,1] range.

[lehins]

Yes, [0, 1] range for Random is also what I had in mind.