Add Tradeking functionality

Yet to be integrated with the Equities flow, hold your horses.

test/tasks/test_tradeking.py

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+from unittest import TestCase
+from datetime import datetime
+from pandas_datareader.data import get_data_yahoo
+from numpy.testing import assert_allclose
+import pytest
+
+from metrik.tasks.tradeking import Tradeking1mTimesales
+from metrik.trading_days import TradingDay
+
+
+@pytest.mark.parametrize('ticker', [
+    'AAPL', 'GOOG', 'SPY', 'REGN', 'SWHC', 'BAC', 'NVCR'
+])
+def test_returns_verifiable(ticker):
+    # Test that the quotes line up with data off of Yahoo
+    now = datetime.now()
+    prior_day = now - TradingDay(1)
+
+    quotes = Tradeking1mTimesales.retrieve_data(prior_day, ticker)
+
+    yahoo_ohlc = map(tuple, get_data_yahoo(ticker, prior_day, prior_day)[
+        ['Open', 'High', 'Low', 'Close']
+    ].values)[0]
+
+    open = high = close = 0
+    low = 999999
+    for index, quote in enumerate(quotes['quotes']):
+        if index == 0:
+            open = quote['opn']
+        if index == len(quotes['quotes']) - 1:
+            close = quote['last']
+        high = max(high, quote['hi'])
+        low = min(low, quote['lo'])
+
+    tradeking_ohlc = (open, high, low, close)
+
+    assert_allclose(tradeking_ohlc, yahoo_ohlc, rtol=1e-3)