Refactoring pln_lik() for readability while checking implementation against Bulmer 1974.
Refactoring pln_lik() for readability while checking implementation against Bulmer 1974.

davharris/macroecotools,weecology/macroecotools,rueuntal/macroecotools,weecology/macroecotools,rueuntal/macroecotools