setup.py fails in environments where locale != *utf8

[sdelafond]

With python3.5, in a "regular" C locale, opening HISTORY.rst fails because that file is utf8-encoded (python2.7 doesn't complain about that).

[Lukasa]

Yup, that seems like a likely problem. Mind supplying a PR to resolve the issue?

[sdelafond]

I was gonna add encoding=utf-8 to the open call, but that won't work in 2.7 unfortunately...

[Lukasa]

@sdelafond You want codecs.open.