ENH: add lbfgs for fitting, but testing shows arima errors
MAINT: improve compatibility with old scipy versions, but some complex number are sneaking in and causing tests to fail
MAINT: more flexibility in setting parameters for fitting
MAINT: for model fitting, let lbfgs use its own fprime approximation instead of passing a separate function that uses finite differences
MAINT: change another fitting default solver from None to 'lbfgs'
MAINT: add keyword to the kalman filter log likelihood calculation function, reducing the amount of side effects of the function when False is passed
MAINT: avoid side effects when computing log likelihood for the estimation of the score or hessian
MAINT: use a mysterious args=(False,) argument instead of using nested function definition
MAINT: add conditional code to support varying versions of scipy fmin optimizers
MAINT: default maxiter 35 -> 50
MAINT: prune dead conditional path
MAINT: track changes to maxiter among layers of code
MAINT: add untested bounds for lbfgsb fitting, and change names from lbfgs to lbfgsb everywhere
MAINT: change the name back
MAINT: finish changing name back
MAINT: remove a warning
MAINT: explicitly check scipy version instead of checking for TypeError
MAINT: avoid storing complex sigma2 during finite-differences score and hessian calculation for mle
Merge pull request #1147 from argriffing/add-lbfgs-fit

ENH: add lbfgs for fitting