Do not byte-encode the proxy address

Byte encoding may crashes with UnicodeEncodeError. And unicode is perfectly valid in domain names.
Tested with python 2.6.8, 2.7.8 and 3.4.2
Fix encoding of intl DNS

IDNA encoding will generate xn-- prefixed byte strings when needed.
Merge pull request #16 from nirgal/master

Fix encodings