Implement teneye

[dmdunla]

Create tensor with ones on the superdiagonal

[DeepBlockDeepak]

Check out tendiag()

[dmdunla]

@DeepBlockDeepak Sorry, I was mistaken about this issue. I now see what teneye is and it is very different than tendiag. I suggest you switch to another "good first issue" for now. I'll think more about this issue and take a look at it myself.