Testing the C-part of tardis

I'm in the process of making a framework that will test the currently untested C-part of TARDIS (the search sorted incident, was a little bit of a wake-up call). 

So @ssim, @mklauser and @orbitfold I need your help - in a couple of ways:

After playing around with C unit testing frameworks and realizing that this is more difficult to integrate into `py.test` (our current testing framework), I think we should wrap each function (this takes a minute) and then test them individually. Now there are still some problems, that maybe either @mklauser or @orbitfold can help with:

We want to make one or more mock rpackets and the question is how do we translate them from python to c and back. Maybe something like this: http://markflorisson.wordpress.com/2011/08/23/memoryviews/?
Having some trouble here with:

```python
In [3]: test = rpacket()
virtual_packet_flag
close_line
d_electron
current_shell_id
nu_line
energy
[1]    30281 illegal hardware instruction  ipython
```

Any ideas @mklauser @orbitfold ?