allow DevDocs floating on top of fullscreen app

[cades]

When I'm working on macOS fullscreen app, launch DevDocs.app will switch to another desktop. This commit make DevDocs.app be able to float on top of fullscreen app.

[egoist]

Hmm but now it will always float on top of almost any app, maybe make this optional?

[cades]

Ok, I will fix that

[egoist]

yeah, like a menu item

[douglas]

Whoa! Would love this feature as I use SublimeText/Atom on fullscreen, iterm2 floating over windows and it would be awesome to have devdocs floating as well =)

[wmertens]

One way to make this less intrusive is to hide when it loses focus.