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)
```
When option `--eof` is used, `trimWhiteSpace` does not get called:
https://github.com/thorade/trimtrailingwhitespaces/blob/issue28_normalizeEOF/ttws/cli.py#L81
I thought that trimming white space and normalizing EOF in one single function would be the most efficient way, but if you prefer this could be seperated.