url: Include username and password as part of URL
Implement username/password support.

Closes chfoo/wpull#30
warc: Fix 'separator' spelling.
url.PercentEncoderMap: Fix missing super() call
Add missing imports. Change tuple return code style.
http.robots: Add missing import.
abstract.client,ftp.util: Add some docstrings.
ftp.client: Remove outdated TODO
http.client: Better docstring.
ftp.command: Split read_stream into begin_stream & read_stream
Rewrite ftp.client interface to align with http.client interface

ftp.client: fetch() pairs with read_contnet(), fetch_file_listing()
pairs with read_listing_content()

processor.ftp: Use of the callback function is eliminated
ftp.command: Accept FTP code 125 on data connection
ftp.client: Add some debug logging
ftp.ls.date.parse_datetime: Fix 12 AM/PM to 24hr logic.
url: Use original string instead of lowercased on schemeless URL

Closes chfoo/wpull#213
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ftp: Catch exception when passive address cannot be parsed.
http.stream_test,scraper.html_test: Add pragma no cover
ftp.ls: Better detection of msdos ls w/o dir
stats: Add debug log