add test_writeout.py to the test suite

Closes #72

I was able to find and install hdf5io related libraries.
Here is the page with detailed install instructions http://pythonhosted.org/neo/install.html
Specifically, I think these are the things that we are missing now to make it work:
```
$ apt-get install libhdf5-serial-dev python-numexpr cython
$ pip install tables
```
The python-neo repo (in case more details are needed): https://github.com/NeuralEnsemble/python-neo

__TODO__: probes with spikes are not yet implemented, so the probe using them was commented out for this test