hist / hist2d inconsistent for plotting single data point

matplotlib version 1.4.2

hist throws an error when fed with a single data point, but hist2d doesn't.

``` python
figure()
hist2d([1], [1]) # works

figure()
hist(1)  # throws a ValueError
```

The error is: "ValueError: x has only one data point. bins or range kwarg must be given"
