Test for `+X11` before using clipboard=unnamedplus
Fix test for 'unnamedplus' again...
Merge branch 'pr/565' into 3.0

Fixes #564, #565
Removed bundle justinmk/vim-sneak
Merge pull request #570 from MattWoelk/3.0

Removed bundle justinmk/vim-sneak
Merge branch 'upstream-3.0' into 3.0