Update lalsimulation import

If lalsim is not installed just add a warning rather than raising an
error. Previously this did already exist in source.py, but we now also
import lalsim in conversion.py as well

tupak/conversion.py

 import tupak
 import numpy as np
-import lalsimulation as lalsim
 import pandas as pd
 import logging
 
+try:
+    import lalsimulation as lalsim
+except ImportError:
+    logging.warning("You do not have lalsuite installed currently. You will "
+                    " not be able to use some of the prebuilt functions.")
+
 
 def convert_to_lal_binary_black_hole_parameters(parameters, search_keys, remove=True):
     """

tupak/source.py

@@ -5,8 +5,8 @@ import logging
 try:
     import lalsimulation as lalsim
 except ImportError:
-    logging.warning("You do not have lalsuite installed currently. You will not be able to use some of the "
-                        "prebuilt functions.")
+    logging.warning("You do not have lalsuite installed currently. You will "
+                    " not be able to use some of the prebuilt functions.")
 
 from . import utils