Merge branch 'develop' into documentation

tests/special_test.py

@@ -0,0 +1,12 @@
+import numpy as np
+import scipy
+import pyerrors as pe
+import pytest
+
+from autograd import jacobian
+from numdifftools import Jacobian as num_jacobian
+
+def test_kn():
+    for n in np.arange(0, 10):
+        for val in np.linspace(0.1, 7.3, 10):
+            assert np.isclose(num_jacobian(lambda x: scipy.special.kn(n, x))(val), jacobian(lambda x: pe.special.kn(n, x))(val), rtol=1e-10, atol=1e-10)