Warning when passing vector as "wb" parameter

[mantiuk]

When passing 3-element vector wb to

merge(files, ... wb=wb):

I get a warning message:

.../HDRutils/merge.py:77: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison
  if wb == 'camera':

The documentation could say in what format the numbers should be passed (numpy array?)