- Switch to pypi.io as Source url

- update to 2.1.0:
* Updated from global requirements
* Update --max-width help
* Add more test coverage for shell formatter
* Add more test coverage for CSV formatter
* Support multiple sub commands in completion
* Factorize more test data
* Factorize some test data
* Factorize common test code
* Factorize argparse importing
* Updated from global requirements
* Updated from global requirements
* Add CLIFF_MAX_TERM_WIDTH envvar to complement --max-width
* Fix prettytable.PrettyTable().max_width wrong usage
* Fix AttributeError when entry point load failed
* Distinguish no existed columns in ShowOne
* Refactor HelpCommand
* Updated from global requirements
* Remove httplib2 from test-requirements.txt
* Sync help message for --help
* handle empty list in table formatter
* Drop Python 2.6 support
* Revert "app,command: disallow abbrev by default"
* Fixes terminal_width on Windows
* Updated from global requirements
* remove openstack-common.conf
* Add doc for deferred_help parameter
* Fix pep8 failure