snnls: double addition of regularization term

[stestoll]

As noted by @mtessmer, ResidualFcn in snnls.py seems to be adding the regularization term twice, once prior to calling _augment, and then again in _augment itself. It should only be once.

Here is the place in snnls.py:

if includePenalty:
    penalty = alpha*L@linfit
    # Augmented residual
    res = np.concatenate((res, penalty))     #    <---  first addition
    res, _ = _augment(res, [], regtype, alpha, L, linfit, huberparam, Nnonlin)    #   <---- second addition

[luisfabib]

I already have applied the appropiate changes on my local copy. After I run a couple of checks, a PR will follow tomorrow.