v1.2.0

• There is now support for transparency, which can be queried or modified
  through the new opacity() function, which functions just like the other
  colour property functions (#4). Opacity (alpha) values are stored as an
  attribute with shade objects, and reflected in the RGB hex representation
  only when less than 1.
• The scalefac() functional has been added, which multiplies its argument just
  as delta() adds it. Both functions now accept, and concatenate, multiple
  arguments for convenience.
• The usual behaviour of the colour property manipulation functions, which
  vectorise over both arguments, can be suppressed by wrapping replacement
  values with the recycle() function, which reverts to a standard R
  "recycling" scheme with final dimensions matching the original.