fix float issues in python 3

test/make_standard_data.py

@@ -15,12 +15,12 @@ sampling_frequency = 4096.
 simulation_parameters = dict(
     mass_1=36.,
     mass_2=29.,
-    a_1=0,
-    a_2=0,
-    tilt_1=0,
-    tilt_2=0,
-    phi_12=0,
-    phi_jl=0,
+    a_1=0.,
+    a_2=0.,
+    tilt_1=0.,
+    tilt_2=0.,
+    phi_12=0.,
+    phi_jl=0.,
     luminosity_distance=100.,
     iota=0.4,
     phase=1.3,