Feature request: ignore whitespaces in pull requests

[siomura]

Hi, I love the new release! It makes reviewing code much easier. I have a feature request: GitHub has the ability to ignore whitespaces in the diffs, but it's not activated by default. It would be great if Octotree exposes an option to enable/disable this in the pull request page. There are some extensions that do this but I don't want to install too many extensions. Octotree is perfect for this I think. Please consider!