ENH: support basinhopping solver in LikelihoodModel.fit()

- new _fit_mle_basinhopping()
- minimizer kwargs can be passed using 'minimizer' kwarg of dict type
base converged flag on res.message in _fit_mle_basinhopping()
use of score and hess arguments in _fit_mle_basinhopping()
update docstring of LikelihoodModel.fit()
TST: new TestProbitBasinhopping
add *args to _check_perfect_pred()
TST: remove no-op callback in TestProbitBasinhopping.setupClass()
Merge pull request #932 from rc/basinhopping

ENH: support basinhopping solver in LikelihoodModel.fit()