fix new_kappa allocation

[alxsrobert]

With the previous script, the allocation of new_kappa using param["kappa"] was interfering with the pointer definition. It was then causing errors in the computation of the new and old likelihoods (new_likelihood then corresponded to the old_likelihood). In outbreaker_find_imports: there was a mistake in the position of the parentheses for the calculation of n_measures.

[finlaycampbell]

Cheers for that @alxsrobert, sorry for slow reply I was away at a conference. Funnily enough I found that bug a couple weeks ago too, turns out I'd only pushed the fix to my own fork and not the main fork! I will be doing a merge of your bug fixes and some of my own additions over the next couple days. Turns out there was actually a theoretical bug in the genetic likelihood itself, which unfortunately may have affected kappa estimates. I will post to the README describing the changes in the likelihood when I merge my fork. Thanks again!

[thibautjombart]

I'll leave this one with you both - thanks! :) Probably stating the obvious, but best make sure that:

• all previous tests are green
• add a new test for this problem specifically
• add @alxsrobert to the list of contributors in DESCRIPTION