commit before turning off synchronous

otherwise python 3.6 fails with
sqlite3.OperationalError: Safety level may not be changed inside a transaction
(fixes issue piskvorky#58)

sqlitedict.py

@@ -368,6 +368,7 @@ def run(self):
         conn.execute('PRAGMA journal_mode = %s' % self.journal_mode)
         conn.text_factory = str
         cursor = conn.cursor()
+        conn.commit()
         cursor.execute('PRAGMA synchronous=OFF')
 
         res = None