Added kron to the doc.

doc/library/sandbox/linalg.txt

@@ -17,4 +17,5 @@ API
 
 .. automodule:: theano.sandbox.linalg.ops
     :members:
-
+.. automodule:: theano.sandbox.linalg.kron
+    :members:

theano/sandbox/linalg/__init__.py

 
+from kron import kron
 from ops import (cholesky, matrix_inverse, solve,
         diag, extract_diag, alloc_diag,
         det, psd, eig, eigh,

theano/sandbox/linalg/kron.py

@@ -2,6 +2,15 @@ from theano import tensor
 
 
 def kron(a, b):
+    """ Kronecker product
+
+    Same as scipy.linalg.kron(a, b) or numpy.kron(a, b)
+
+    :param a: array_like
+    :param b: array_like
+    :return: array_like with a.ndim + b.ndim - 2 dimensinos.
+
+    """
     a = tensor.as_tensor_variable(a)
     b = tensor.as_tensor_variable(b)
     if (a.ndim + b.ndim <= 2):