photobiology (Bug fix and compatibility update)

Preview of future CRAN version 0.9.6.

Make compatible with next version of package ‘dplyr’ (> 0.4.3) and new package ‘tibble’ (>=0.1.0).
Fix bug in indexing of "object_spct" objects.
Add a few missing warnings for out-of-range data in the values returned by operators and maths functions.

Please, report any problems you encounter, and suggest possible changes or additions to the functionality!

NOTE: The package preview is now available from the R-respository at this site.