Doesn't support photo_view 0.12.0 and up

I am getting this error when I update to a stable photo_view version which is 0.12.0 

Error Message
```
Because gallery_view 1.0.0+1 depends on photo_view ^0.11.1 and no versions of gallery_view match >1.0.0+1 <2.0.0, gallery_view ^1.0.0+1 requires photo_view ^0.11.1.
So, because nathanhr depends on both photo_view ^0.13.0 and gallery_view ^1.0.0+1, version solvin
```g failed.
