[question] possible to use compound logic in indexing
in your documentation, you have the following example:

```
  >>> df[df['A'] > 0.5]
                         A              D              N              S
  2009-05-29 00:00:00    0.979307       0.979307       4              5
  2009-07-31 00:00:00    0.536261       nan            6              5
  2009-09-30 00:00:00    0.537841       nan            8              5
```

would it be possible to do something like this:

```
  >>> df[df['A'] > 0.5 and df['N']>5] 
```

where both conditions are satisfied? The syntax supports it, but I'm not getting what I expect.
