Fix UnicodeEncodeError issue by encoding string as UTF-8

[gildasio]

Closes #193

I had a problem similar to #193 but using HTTP authentication, that's why I fix in these two places, maybe there are more places to fix, but I did not check all of it.

Here is how pycurl handles unicode:

• http://pycurl.io/docs/7.19.5.3/unicode.html