Improve unicode safety
- Do not assume utf-8 encoding for Picture filenames
- Add `to_str()` and `to_unicode()` for eas(y|ier) conversion
Use correct line width in stimuli.Line() (#2)
Merge remote-tracking branch 'upstream/master'
Update reference from CHANGES.txt to CHANGES.md in setup.py
Merge pull request #4 from smathot/master

Fix unicode bug in Picture()