Add example.py

This adds an executable example so users can easily invoke:

```bash
python example.py
```

and reproduce the output in the screenshot in the `README.md`:

```bash
$ python example.py
+----------------+-----+----------+
| Name Of Person | Age | Nickname |
+================+=====+==========+
| Mr             |     |          |
| Xavier         |  32 |          |
| Huon           |     |   Xav'   |
+----------------+-----+----------+
| Mr             |     |          |
| Baptiste       |   1 |          |
| Clement        |     |   Baby   |
+----------------+-----+----------+

 text     float       exp      int     auto
==============================================
abcd      67.000   6.540e+02    89   128.001
efghijk   67.543   6.540e-01    90   1.280e+22
lmn        0.000   5.000e-78    89   0.000
opqrstu    0.023   5.000e+78    92   1.280e+22
```

![texttable results](http://i.imgur.com/Zu7FB.png)