Updating models to allow normal imports

This updates the python for all the models to allow normal importing in python3. There should not be any impact on the running of the model; everything will function as it did before, but the imports follow standard python rules instead of the slightly weird standards they did before.

In addition, there's a helper script that's been added to automatically update a model to make it importable, and there's a piece of the pre-commit hook that's been added to test if the models are all import-compatible.

PLUGIN/MadSTR/__init__.py

@@ -8,13 +8,13 @@
 #                                                   #
 #####################################################
 
-from . import os
-from . import sys
+import os
+import sys
 root_path = os.path.split(os.path.dirname(os.path.realpath( __file__ )))[0]
 sys.path.insert(0, root_path)
 
-from . import MadSTR.madstr_interface as madstr_interface
-from . import MadSTR.madstr_exporter as madstr_exporter
+import MadSTR.madstr_interface as madstr_interface
+import MadSTR.madstr_exporter as madstr_exporter
 ##import Resummation.resummation_exporters as resummation_exporters
 
 # Three types of functionality are allowed in a plugin