add additional note for setting curve_fit tolerance

Author: TomDonoghue

fooof/objs/fit.py

@@ -201,6 +201,7 @@ def __init__(self, peak_width_limits=(0.5, 12.0), max_n_peaks=np.inf, min_peak_h
         # The maximum number of calls to the curve fitting function
         self._maxfev = 5000
         # The tolerance setting for curve fitting (see scipy.curve_fit - ftol / xtol / gtol)
+        #   Here reduce tolerance to speed fitting. Set value to 1e-8 to match curve_fit default
         self._tol = 0.00001
 
         ## RUN MODES