Issue28 normalize eof

This implements EOF normalization, as requested in #28 
I implemented it as a new command line option `--eof`, but one could also discuss if EOF normalization should be performed always when trimming white space.
The code that actually does the EOF normalization is 
```python
            while len(lines) > 1 and not lines[-1]:
                lines.pop(-1)
```
I think that it is better to always normalize the EOF. 
That makes the implementation also a lot easier, it is just two lines.
Will send a new pull request in a couple of minutes