Individual symbol ticker stream to websockets.

Merge pull request sammchardy#639 from adanikel/new/missing_subaccoun…

…t_endpoints

New/missing subaccount endpoints

Merge pull request sammchardy#534 from bsliran/patch-1

Updates the get_product endpoint

Merge pull request sammchardy#623 from ttamg/feature/websockets-for-i…

…solated-margin

Added websockets functionality for isolated margin accounts

Merge pull request sammchardy#616 from xulngx/feature/get_isolated_ma…

…rgin_account

Update client.py