Update snippet based on selection

[danirabbit]

Fixes #12

[jeremypw]

1. Clicking on a symbolic icon child after a color icon results in two selected items. Even though one is unfocused this still looks wrong/confusing to me.
   

2. If the icon name is changed after selecting an icon size and type, the icon size and type reverts to the default of 24px color. I think the selected size and type should persist (if available).

3. After selecting an icon size for "emblem-documents" then change to a different icon name the icon sizes are no longer selectable. This can happen with other icons but the exact reason is unclear - possibly due to unavailable color icons?

4. Emote icons do not have a "24px" version; nevertheless the code snippet is for 24px

[danirabbit]

@jeremypw

1, 3, and 4. Fixed!
2. I think this would require a substantial rewrite since currently when we change icons we destroy all the flowbox children and rebuild them. I think it's a big enough change that it should be left for a future branch

[zeebok]

This looks good to me, and addresses the issues Jeremy spotted. If you like I can approve.

Haven't heard back in a couple weeks and someone else confirmed this fixed raised issues