write_frame fails to replace table (io.sql)
For the option if_exists='replace' in write_frame the table is dropped but not re-created.
Simple error in the logic:

```
#create or drop-recreate if necessary
create = None
if exists and if_exists == 'replace':
    create = "DROP TABLE %s" % name
elif not exists:
    create = get_schema(frame, name, flavor)

if create is not None:
    cur = con.cursor()
    cur.execute(create)
    cur.close()
```
