Allow custom info columns in counts table.

libcodonusage/libcodonusage.py

@@ -280,16 +280,18 @@ might be excluded.
 
 def make_counts_only(
         counts_table,
-        seq_id_kw="locus_tag", alt_tag_kw="old_locus_tag"):
+        seq_id_kw="locus_tag", alt_tag_kw="old_locus_tag",
+        ref_info_cols=None):
     """
     Integrate "informative" columns of *counts_table* into the index.
     """
     # To ensure a stable order:
-    ref_info_cols = [
-        alt_tag_kw, seq_id_kw,
-        "start", "end", "length",
-        "start_codon", "expected_start_aa",
-        "first_stop", "nb_stops", "start_upstream", "end_downstream"]
+    if ref_info_cols is None:
+        ref_info_cols = [
+            alt_tag_kw, seq_id_kw,
+            "start", "end", "length",
+            "start_codon", "expected_start_aa",
+            "first_stop", "nb_stops", "start_upstream", "end_downstream"]
     # To ensure no info columns are lost:
     info_cols = [
         counts_table.index.name,