DOC - ADD doc and how to on select from select
Add documentation and how to on select in select.
>>> from py_linq_sql import SQLEnumerable
>>> from tmp_connection_psql import tmp_connection
>>> with tmp_connection("dummypassword", "./create_db_for_main.sql") as con:
... sqle_1 = SQLEnumerable(con, "objects")
... sqle_2 = SQLEnumerable(con, sqle_1)