n-st created a pull request in webrender/trello-collapse-lists

Subtle toggle icon + Only show toggle icon when hovering over list header

*Part of a set of PRs: subtle icons #3, autohiding #4, or both #5.* This PR combines #3 and #4: use a subtle toggle icon, and only show it when the mouse is hovering over a list header.
02 27, 2019