- Testing:

  - Write quickcheck properties for Text.Trans.Tokenize!

- Widgets:

  - Scrollable area (a generalization of the List) which can wrap a
    widget and make it scrollable in a confined space.  To make this
    work, we may need masking support in Vty.  Scrolling is really
    just (top, left, widget, mask window size) where the window size
    depends on available space and top/left positions are modified by
    the application as scrolling requests are received.

  - horizontal / vertical boxes which can take absolute values or
    percentages to determine how to allocate space to their children
    (this may entail re-tooling the existing types to take one of
    various space allocation specifiers).  Maybe something like:

    Size = Absolute Int Int
         | Percent Int
         | Auto
    sizedHBox :: Widget -> Widget -> Size -> Widget

    Sizing policy (Size) determines how a box reserves space for each
    of its two children.  Percent a implies (100-a) percent space
    allocated for one child.  Absolute a b implies a rows or columns
    for the "first" child and b rows or columns for the "second"
    child.  Auto implies that the box may grow to accomodate the size
    of its children.

  - table widget for laying out name/value pairs in nice format

  - support for right-aligning text (just left-padding?)