Parallelising spin evolution

The purpose of this MR is to speed up the spin evolution calculation by running on multiple cpus.

pesummary/gw/file/evolve.py

@@ -71,7 +71,7 @@ def evolve_spins(
         number of cores to run on when evolving the spins. Default: 1
     evolve_approximant: str
         name of the approximant you wish to use to evolve the spins. Default
-        is SpinTaylorT5
+        is SpinTaylorT5. Other choices include SpinTaylorT1 or SpinTaylorT4
     """
     if isinstance(final_velocity, str) and final_velocity.lower() == "isco":
         final_velocity = 6. ** -0.5
@@ -152,8 +152,7 @@ def _evolve_spins(
     dt: float
         steps in time for the integration, in terms of the mass of the binary
     evolve_approximant: str
-        name of the approximant you wish to use to evolve the spins. Default
-        is SpinTaylorT5
+        name of the approximant you wish to use to evolve the spins.
     """
     if np.logical_or(a_1 > tolerance, a_2 > tolerance):
         # Total mass in seconds