Tastyworks

Changed
- Changed the underlying streamer connection to use `aiocometd` rather than our own, custom-rolled
transport.

Added
- The `time-in-force` and `gtc-date` properties to the OrderDetails object

Changed
- Example script now uses env vars for TastyWorks username/password instead of hard-coding values.

Added
- The `rejected` order status type

Changed
- Fixed bug with in the `Quote` mapped item to support the new time fields
- Removed the `time` key from the `Quote` mapped item
- Fix bug for missing `price` field in the `Order` model

Changed
- Changed number formats to use decimal types instead of floats for predictable representations

Changed
- Fixed a bug which prevented orders from executing altogether... big one.

Removed
- The `underlying_symbol` field from the `Order` model, this is not necessary and tastyworks does not have
the symbol tied to an order; they are tied to individual legs of the order.

Added
- Added a new, rewritten `get_option_chain` method to the `Underlying` model, which is inherited by
models like `Stock` and all other future representations of securities.
- New `Security` model representing all securities (options and underlyings).
- New `Underlying` model representing all underlyings (stocks, indices, ETFs).
- New `OptionChain` model which represents an option chain (a collection of options). This should make
management of a list of related options (i.e. for a ticker) easier.

Removed
- The `get_option_chains` function from the TastyAPISession.
- The `Model` model