Version 1.5.0

• The writeNifti() and writeAnalyze() functions gain a "compression"
  argument to control the compression level used when writing gzipped images.
• The viewer will now show 4D images with fourth dimension 3 as vectors if the
  RNifti.d4vectors option is TRUE. This is off by default (following the
  previous behaviour) as it's less explicit than an image with a vector intent.
• The niftiHeader() function will no longer call asNifti() on an argument
  that looks like a path, as this will wastefully read in the pixel data when
  only the metadata is needed.
• Support for MriImage objects with complex or RGB types has been added.
• cfloat and cdouble are now additionally accepted as datatypes for 32-bit
  and 64-bit floating-point complex types, respectively.
• The upstream NIfTI libraries have been updated.