* 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.
* GH-270: Make line spacing configurable via the 'Appearances' preferences pane.
* GH-322: Fix crashes related to the file browser.
* Bugfix: The command line tool `vimr` sometimes does not open the files in the frontmost window.