Make bounds() not optional and as a var

[JoachimM7]

Two suggestions:

1. Why is bounds() optional? It's a little bit annoying always to unwrap it. Only in the Image-class there is the possibility, that there will be no Rect as a return. So maybe you could only make this one optional?

2. As in the newer Swift-versions it would be nicer, if bounds is a property and not a function?

[ystrot]

Thanks for your comments! I agree with you, but it actually makes implementation much more complicated. However we decided to provide quick and working solution for now and then make it optimal. Regarding property/method - I don't think it makes a lot of sense. It can't be assigned and implementation looks too complicated for a "property".

I'm closing this ticket and if you have more comments please let's keep discussion in a single place here: #252