mrdna script now recognizes list files for model creation

bin/mrdna

@@ -100,6 +100,8 @@ def main():
         from mrdna.readers import read_vhelix as read_model
     elif extension == '.pdb':
         from mrdna.readers import read_atomic_pdb as read_model
+    elif extension == '.dat' or extension == '.txt':
+        from mrdna.readers import read_list as read_model
     else:
         raise Exception("Unrecognized input file '{}'".format(infile))
     model = read_model( str(infile), debye_length=args.debye_length, temperature=args.temperature )