ENH: Add Series.histogram()
Should I write a `Series.histogram` that calls `numpy.histogram` and returns a new Series of counts indexed by bins?

```
In [4]: s = Series(randn(100))

In [5]: counts, bins = np.histogram(s)

In [6]: Series(counts, index=bins[:-1])
Out[6]: 
-2.968575     1
-2.355032     4
-1.741488     5
-1.127944    26
-0.514401    23
 0.099143    23
 0.712686    12
 1.326230     5
 1.939773     0
 2.553317     1
dtype: int32
```

...would be accomplished by...

```
Series.histogram()
```

which would accept at the arguments that `np.histogram` accepts (e.g., choosing bins manually, specifying number or range of bins, etc.).

from http://stackoverflow.com/a/17150734/1221924

The proposed method doesn't save all that much typing, but it would help users discover this convenient way of storing a histogram. Proceed?
