IArray and IMap iterators now yields references

[cecton]

Fixes #60

[kirillsemyonkin]

does into_iter() provide Ts or &Ts? maybe would be nice to mirror Vec's behavior where iter() gives &T and into_iter() gives T

[cecton]

oh wow, so iter() returned owned objects and into_iter() returned references? I did not even implemented that into_iter() stuff xD

[kirillsemyonkin]

Is there a need for a custom IArrayIter<'a, T>? Is std::slice::Iter via Deref<Target = [T]> not enough?

[cecton]

I couldn't make it work but feel free to try.

The into_iter() for IMap is also more complicated than I expected. I don't use map anyway so I would prefer to leave it for later and merge what works for now.

[cecton]

I misunderstood IArrayIter with IArrayIntoIter my bad. Well great if it works!

Ready to merge without the map into_iter?