Limit resize size by size of original

[dbigunyak]

It's possible to send request with size bigger than original. Much more bigger:
ll 133/fc3cb123-cf43-45d3-822f-472aa84f5389_546e81b73d4fbe9472b041afd9723227_1x1_41400x57600.jpeg -h
-rw-r--r-- 1 www www 46M Oct 17 13:27 fc3cb123-cf43-45d3-822f-472aa84f5389_546e81b73d4fbe9472b041afd9723227_1x1_41400x57600.jpeg

You can easily use this to overflow cache partition.
Wise solution will be - return original size if requested sizemore than original

[shifr]

Hi Dima,
I've noticed that this is an issue for https://github.com/shifr/vips and duplicated it here shifr/vips#2. I've just fixed it up and now you only need to update this package with go get -u github.com/shifr/vips and get the latest release of imgwizard