Sptensor wrong check.

[gaurush-hiranandani]

In line 71 of sptensor.py, I believe the condition to check should be len(subs) == len(vals). The reason is that we want to check the number of provided subscripts to be equal to the number of values. Currently, it is checking the dimension of the tensor to be equal to the number of values which probably isn't right. Although, it works in the provided example because the dimension, the subscripts, and the values are all three. Correct me, if I am wrong.