 numpy FutureWarning in df.equals
From the example in the v0.13.1 whatsnew docs (http://pandas.pydata.org/pandas-docs/version/0.15.0/whatsnew.html#id12):

```
df = DataFrame({'col':['foo', 0, np.nan]}).sort()
df2 = DataFrame({'col':[np.nan, 0, 'foo']}, index=[2,1,0])
df.equals(df)
```

gives:

```
In [3]: df.equals(df)
C:\Anaconda\lib\site-packages\numpy\core\numeric.py:2367: FutureWarning: numpy e
qual will not check object identity in the future. The comparison did not return
 the same result as suggested by the identity (`is`)) and will change.
  return bool(asarray(a1 == a2).all())
Out[3]: True
```

The example in basics.rst section does not have this warning (http://pandas.pydata.org/pandas-docs/version/0.15.0/basics.html#comparing-if-objects-are-equivalent):

```
df = DataFrame({'one' : Series(randn(3), index=['a', 'b', 'c']),
                'two' : Series(randn(4), index=['a', 'b', 'c', 'd']),
                'three' : Series(randn(3), index=['b', 'c', 'd'])})
(df+df).equals(df*2)
```
