touchList padding makes gems too tall

The padding we added to touchList makes items with icon gems too tall.

![tall](http://i.imgur.com/EpYFO9i.png)

To fix, we just need to set `$H_gem` to be 24px instead of 32px. This also makes gems square, which is nice.

![square](http://i.imgur.com/vw6mFsn.png)