Add support for index_col

[richbeales]

In query you call through to pd.io.sql.read_sql() but don't provide a way of passing in the index_col you want to use. Can this be added to the method signature?

[glamp]

yep that should be easy

[ueg1990]

How would this be done? dont u have to add index_col parameter in every init function and then do self.index_col = index_col (where default of index_col will be None)? and then pass self.index_col to pd.io.sql.read_sql() ?