OrderBook fix

[michaelsimonelli]

NOTE OrderBook is setting product_id as string, which sets the inherited WebsocketClient.products as string, but WebsocketClient.products is type string array

Causes issues with OrderBook property: def product_id(self): As it's selecting the first char of the string instead of first element in array. e.g. The product_id='BTC-USD', returns 'B' when the getter is called.

May have some other side effects in the code, but this is first I noticed

OrderBook Excerpt

class OrderBook(WebsocketClient):
    def __init__(self, product_id='BTC-USD', log_to=None):
        super(OrderBook, self).__init__(products=product_id)
        self._asks = SortedDict()
        self._bids = SortedDict()
        self._client = PublicClient()
        self._sequence = -1
        self._log_to = log_to
        if self._log_to:
            assert hasattr(self._log_to, 'write')
        self._current_ticker = None

    @property
    def product_id(self):
        ''' Currently OrderBook only supports a single product even though it is stored as a list of products. '''
        return self.products[0]

WebsocketClient Excerpt

    def _connect(self):
        if self.products is None:
            self.products = ["BTC-USD"]
        elif not isinstance(self.products, list):
            self.products = [self.products]