readme.rst: Fixes typo in archiving example.
Fixes ProgressRecorderSession to print to correct stream.

Closes chfoo/wpull#15.
setup.py: Removes requiring 3to2. readme: Emphasize need latest 3to2.
url.py: Defaults to Latin-1 quasi_quote, quasi_quote_plus.

Callers of the quasi quote functions should use is_percent_encoded() to
determine if the quasi quote function is suitable.
Adds percent-encoded URL to test file.
writer.py: Uses quasi_quote() as appropriate.
http.Request.new: Supports url_encoding parameter.
processor,robotstxt: Passes the URL encoding to the Request factory.

Closes chfoo/wpull#16.