Add type conversion for Panda's Timestamp

Add type conversion for Panda's Timestamp, if Panda library is present in system
(thanks for this project, I was about to do the same thing from scratch)

sqlite_utils/db.py

@@ -8,6 +8,12 @@ import pathlib
 
 SQLITE_MAX_VARS = 999
 
+
+try:
+    import pandas as pd
+except ImportError:
+    pd = None
+
 try:
     import numpy as np
 except ImportError:
@@ -64,6 +70,13 @@ if np:
         }
     )
 
+# If pandas is available, add more types
+if pd:
+    COLUMN_TYPE_MAPPING.update(
+        {
+            pd.Timestamp: "TEXT"
+        })
+
 
 class AlterError(Exception):
     pass