Add @ operator for dot product about sparse HOT 5 CLOSED

diff --git a/sparse/core.py b/sparse/core.py
index be9c06c..1c8ee4b 100644
--- a/sparse/core.py
+++ b/sparse/core.py
@@ -328,6 +328,8 @@ class COO(object):
     def dot(self, other):
         return dot(self, other)

+    __matmul__ = dot
+
     def reshape(self, shape):
         if self.shape == shape:
             return self
diff --git a/sparse/tests/test_core.py b/sparse/tests/test_core.py
index e531245..15b44aa 100644
--- a/sparse/tests/test_core.py
+++ b/sparse/tests/test_core.py
@@ -1,5 +1,6 @@
 import pytest

+import sys
 import random
 import operator
 import numpy as np
@@ -136,6 +137,9 @@ def test_dot():
     assert_eq(a.dot(b), sa.dot(sb))
     assert_eq(np.dot(a, b), sparse.dot(sa, sb))

+    if sys.version_info >= (3, 5):
+        assert_eq(a @ b, sa @ sb)
+

 @pytest.mark.parametrize('func', [np.expm1, np.log1p, np.sin, np.tan,
                                    np.sinh,  np.tanh, np.floor, np.ceil