`has_table` does not work for table names that need escaping

[rad-pat]

has_table method does not works for tables/schemas with characters that need escaping e.g. test-schema, test-table

Current code uses EXISTS TABLE schema.name, this doesn't appear to work if table name needs escaping.

Suggest use of information_schema like e.g. get_columns

def has_table(self, connection, table_name, schema=None, **kw):
    full_table = table_name
    query = """
        select 1
        from information_schema.columns
        where table_name = '{table_name}'
    """.format(
        table_name=table_name
    )

    query = "{query} and table_schema = '{schema}'".format(
        query=query, schema=schema
    )
    result = connection.execute(text(query))
    return bool(result.first())

[rad-pat]

Fixed with #27