Add CBOE Optionable list

test/tasks/test_cboe.py

@@ -0,0 +1,12 @@
+from unittest import TestCase
+
+from metrik.tasks.cboe import CboeOptionableList
+
+
+class CboeTest(TestCase):
+
+    def test_optionable_list(self):
+        companies = CboeOptionableList.retrieve_data()['companies']
+        assert len(companies) > 2000
+        # TODO: Get lists of companies from ETF holdings and verify that they
+        # can be found here as well - this should be a superset