Some maintainers for different linux distribution are having some
problems with the encoding on different python versions. This change
intents to make all python files define explicitly the encoding, license
and unix line separators. Remove one example of the README.rst file
where a possible non UTF-8 character is used.
Negative amounts were not working (when no currency is used), because
`get_digits` method does not expect `-` sign, which crashes conversion.
To avoid that, we split minus sign from number string and prepare its
word to be used with amount words.
closes: #184
