Render all stylesheets in atom-styles elements without contexts

Signed-off-by: Nathan Sobo <nathan@github.com>
W/o shadow-dom, don't add global atom-styles element for text editor

Signed-off-by: Nathan Sobo <nathan@github.com>
Fix autocomplete specs
Merge pull request #4101 from atom/mb-fix-styles

Fix user stylesheet regression due to shadow DOM PR