NIST: spectral lines not showed

Hello,

Thanks for providing a python based query to NIST. I think this will help me a lot. 

I am facing a problem and I do not know if it is a bug with the code or with the user (in this case, myself). There are some spectral lines that the query to don show. For example, I did this query:

```python
In [55]: table =  Nist.query(4000 * u.nm, 4200 * u.nm, linename="O II", wavelength_type='vac+air')

In [56]: print table
```
```
Observed   Ritz  Rel.   Aki   Acc.       Ei           Ek                Lower level                  Upper level          Type    TP    Line
-------- ------- ---- ------- ---- ---------------------------- ---------------------------- ---------------------------- ---- ------- -----
      -- 4146.29   --  3730.0    D 32.147565    -     32.446508 2s2.2p2.(1D).4s | 2D   | 5/2 2s2.2p2.(3P).5p | 2D*  | 3/2   -- T5723LS L7243
      -- 4147.08   -- 33500.0    C 32.147622    -     32.446508 2s2.2p2.(1D).4s | 2D   | 3/2 2s2.2p2.(3P).5p | 2D*  | 3/2   -- T5723LS L7243
```

And I got just this two lines when NIST shows me a lot more. Why? Have I missed something?