* GH-309: When opening a file via a GUI action, check whether the file is already open.
    - Open in a tab or split: select the tab/split
    - Open in another (GUI) window: let NeoVim handle it.
* GH-239, GH-312 Turn on font smoothing such that the "Use LCD font smoothing when available" setting from the General system preferences pane is respected.
* Update RxSwift from `3.0.0-rc.1` to `3.0.0`.