Bug comment: commented out code, weigths don't sum to 1 see #1845
REF: _fit_newton add Ridge correction to Hessian, see also #953
REF: _fit_newton, add ridge_factor option, default 1e-10
REF _fit_newton use np.asarray(hess)
Merge pull request #1847 from josef-pkt/newton_regularize

REF regularize optimize._fit_newton (ridge factor)
Change bare asserts to numpy asserts
Fix assert
Merge pull request #1851 from kshedden/cor_nearest_maint

TST: Cor nearest factor tests
BLD: Don't hard-code path for building notebooks. Closes #1249
_spg_optim returns history of objective function values
Merge pull request #1854 from jseabold/fix-path

BLD: Don't hard-code path for building notebooks. Closes #1249
Merge pull request #1856 from kshedden/cor_nearest_maint2

REF/TST _spg_optim returns history of objective function values
TST: disable test failing with scipy 0.14.0
Merge pull request #1865 from josef-pkt/disable_tst_distribution_1864

TST Disable test distribution see #1864
ENH: add cov_type to Regression model.fit(), first version
DOC: covtype in fit: update example with cluster
BUG: use use_t argument
REF: base Model, new optional attribute df_resid_inference
TST: robustcov add test for fit options and for scale, rsquared
     fix example
Merge pull request #1867 from josef-pkt/REF_covtype_fit

ENH/REF add covtype choice to fit method