pandas.Series.__eq__ is broken for series with different index
Something seems to be wrong with s1 == s2 when s1 and s2 don't have the same index. Here is a snippet example:

``` python
import operator
import pandas
s1 = pandas.Series([1,2], ['a','b'])
s2 = pandas.Series([2,3], ['b','c'])
s1 == s2
s2 == s1
```

with the output:

```
InIn [5]: s1 == s2
Out[5]: 
a    False
b    False

In [6]: s2 == s1
Out[6]: 
b    False
c    False
```

On the other hand using combine works fine:

```
In [7]: s1.combine(s2, operator.eq)
Out[7]: 
a    0
b    1
c    0

In [8]: s2.combine(s1, operator.eq)
Out[8]: 
a    0
b    1
c    0
```

I guess you can first align s1 and s2 and then compare them, but is there a good reason why this couldn't work out of the box?

There doesn't seem to be any tests for pandas.Series. __eq__ for two series with a different index in pandas/pandas/tests/test_series.py. I have a patch lying around to add such a test and I could commit it if that's useful.
