Initializes a new tensor.

// Defines a 2x2x2 tensor [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]
let A = Chalkboard.tens.init([[1, 2], [3, 4]],
[[5, 6], [7, 8]]);
let B = Chalkboard.tens.init([[[1, 2], [3, 4]],
[[5, 6], [7, 8]]]);