Unsupported emojis can overflow their divs

[gfxholo]

Some new emojis consist of two older emojis combined by a ZWJ character. This makes emojis more backward compatible with older systems, but the plugin doesn't handle the extra width very well.

Examples: Windows 10 (which only supports Emoji 12)

Sidebar tabs are a good case study for a solution:

[gfxholo]

This looks better around the app now. Still goofy, but at least the goofiness is contained.