Mistake in BinOp.conform?
in BinOp.conform in pandas.computation,pytables there is this code:

```
    def conform(self, rhs):
        """ inplace conform rhs """
        if not com.is_list_like(rhs):
            rhs = [rhs]
        if hasattr(self.rhs, 'ravel'):
            rhs = rhs.ravel()
        return rhs
```

I think this is wrong.  The first test checks `rhs`, but the second checks `self.rhs`.  They should both check one or the other.  I _think_ both should check local `rhs` but I'm not really familiar with all the nuts and bolts here so I'm not sure.

This causes failures when doing HDF5 queries making use of a local variable whose value is a single Numpy value (e.g., a float64).  Because even a single numpy value has `ravel`, but it is not list-like, both `if` blocks execute, meaning that it sets `rhs` to a list and then tries to call `ravel` on it.  This leads to a difficult-to-debug error because the exception is caught at a higher level and replaced with an "Invalid query syntax" error message.
