Compatibility with pandas 0.23.3

[jgrady-omico]

I'm using pandas 0.23.3 and pysqldf is not compatible - the flavor argument for to_sql has been removed, so the call fails.

I've edited the code in _write_table of pysqldf/sqldf.py to read
to_sql(df, name=tablename, con=self.conn, dtype=dtype)
instead of
to_sql(df, name=tablename, con=self.conn, flavor="sqlite", dtype=dtype)
which corrects the problem for this version of pandas. I guess a try/except would fix it generically?