added test file and test get_leaderboard

Author: bernardobraga92

tests/test_cryptoapi.py

@@ -0,0 +1,13 @@
+import pytest
+
+import numerapi
+
+
+@pytest.fixture(scope='function', name="api")
+def api_fixture():
+    api = numerapi.CryptoAPI(verbosity='DEBUG')
+    return api
+
+def test_get_leaderboard(api):
+    lb = api.get_leaderboard(1)
+    assert len(lb) == 1