Fixed install fail by renaming a file

Hello,

First of all, this did not happen via pip, but via this git repo.

```python setup.py install``` fails with the following error message : 

```error: can't copy 'man/ansi2html.1': doesn't exist or not a regular file```

In setup.py, the data_files argument has ```man/ansi2html.1``` but the actual file is ```man/ansi2html.1.txt```

Fixed by renaming the file correctly