Version 1.7.0

• Indexing into an rgbArray or an RGB-valued internalImage now produces a
  result of type rgbArray, to maintain the special interpretation of these
  values, and facilitate conversion to strings.
• rgbArray now also gains an as.raster method.
• The test suite has been moved from testthat to tinytest.
• An API accommodation for versions of R before 3.1.0 has now been removed, as
  it produces a note in the current R-devel.