added a custom entry for calculating fitness
dialyzer fix
introduced a nif custom entry for fitness calculation
fixed the code path and changed default fitness entry
added locks for thread safety
removed the custom ETS fitness entry
pleasing Elvis and mpmiszczyk
pleasing Elvis part II
pleasing mpmiszczyk part II
Merge pull request #8 from ParaPhraseAGH/nif_fitness_entry

Managing fitness logs with a NIF entry