Use RStudio Viewer Window When Available Instead of Browser

[brodieG]

As per Noam Ross.

[timelyportfolio]

I'll be happy to help here. Would it be ok to add htmltools dependency? diffobj already requires rmarkdown which requires htmltools so guessing it if fine. Then you could replace html.R using htmltools `tags which easily plug into RStudio.

[brodieG]

My initial inclination is to avoid doing so. The markdown dependency is a suggests as opposed to an imports. I'm not completely opposed, but would want to first believe that doing the integration without htmltools is difficult. In the little research I did it seemed straightforward.

I'm trying to keep the import dependency list small. Right now the only non-base dependency is crayon, and I submitted a PR to crayon to remove dependencies that it had that were not strictly necessary.

If you are willing to address this without htmltools then by all means. I started working on it a little bit so I can push the branch for you. Otherwise you can wait for me to bang my head on this a bit and see how it goes.

[brodieG]

Actually, the basic implementation was super easy. It's working already. Need to think about how to handle the inset vs. maximized sizes though since the standard small screen of the viewer is no good with the default width settings.

[brodieG]

The viewer branch has output go to the RStudio viewer. I haven't tested much at all though.