Release v0.4.1

Version 0.4.1 (2021-06-10)

This is a minor patch with new features, bug fixes, and pending deprecations.

New Features

• Switched to using banded solvers for all Whittaker-smoothing-based algorithms
  (all functions in pybaselines.whittaker as well as pybaselines.morphological.mpls),
  which reduced their computation time by ~60-85% compared to version 0.4.0.
• Added pentapy as an optional dependency. All Whittaker-smoothing-based functions
  will use pentapy's solver, which is faster than SciPy's solve_banded and solveh_banded
  functions, if pentapy is installed and the system is pentadiagonal (diff_order is 2).
  All Whittaker functions with pentapy installed take ~80-95% less time compared to
  pybaselines version 0.4.0.

Bug Fixes

• The alpha item in the dictionary output of whittaker.aspls is now the full alpha
  array rather than a single value.
• The weighting for several Whittaker-smoothing-based functions was made more robust
  and less likely to create nan weights.

Other Changes

• Increased the default max_iter for whittaker.aspls to 100.

Deprecations/Breaking Changes

• The constant pybaselines.utils.PERMC_SPEC is no longer used. It will be removed
  in version 0.6.0.