astrobase v0.4.1

New stuff

• periodbase.kbls: now returns BLS stats along with the period finder results.

• varbase.trends: added External Parameter Decorrelation with arbitrary
  external parameters, optimizer function, and objective function.

• periodbase: added a wrapper for the Transit Least Squares period-finder
  (Hippke & Heller 2019; added by @lgbouma)

• periodbase.zgls: added calculation of the analytic false-alarm probability.

• services.gaia, services.mast: added single-object search-by-name
  functions.

• lcfit.utils: added an iterative_fit function.

Changes

• lcproc.tfa: now removes template objects from consideration if they're too
  close to the target object.

• periodbase: broke out all of the functions in periodbase/__init__.py to
  periodbase/utils.py and periodbase/falsealarm.py as appropriate.

Fixes

• periodbase: fixed epsilon checking against values of previous best periods
  when iterating through periodogram peaks (by @joshuawallace).

• periodbase.zgls: now correctly uses tau in the calculation of the
  periodogram value.

• varclass.starfeatures: fixed missing and in an if-statement (by
  @joshuawallace).

• lcproc.tfa: various bug-fixes.