ENH: support index=True for SQL io.sql.get_schema
`pd.io.sql.get_schema` can be used to see the schema 'create table' statement. This function should support including the index (which is actually the default for `to_sql`)

```
In [31]: df = pd.DataFrame({'col':[1,2,3]}, index=pd.date_range('2012-01-01', periods=3))

In [33]: print pd.io.sql.get_schema(df, 'test_schema', con=engine_postgres)

CREATE TABLE test_schema (
    col BIGINT
)

In [34]: print pd.io.sql.get_schema(df.reset_index(), 'test_schema', con=engine_postgres)

CREATE TABLE test_schema (
    index TIMESTAMP WITHOUT TIME ZONE, 
    col BIGINT
)
```
