Minor change: tensor.ones and tensor.zeros can accept single integer arguments

Currently, tensor.ones and tensor.zeros require their shape argument to be a list or tuple. However, numpy.ones/numpy.zeros accepts a single integer:

```python
numpy.ones(3) # [1, 1, 1]
tensor.ones(3).eval() # ERROR
tensor.ones([3]).eval() # [1, 1, 1]
```

This PR is a very minor change to bring theano/numpy syntax back in line and allow these integer arguments.