AutoUpgrade 0.3.0

Changelog

• Fork of autoupgrade (https://pypi.python.org/pypi/autoupgrade).
• Python 3 support.
• Removed unnecessary dependencies.
• Pre-release and force-reinstall support.
• Massive code refactoring and cleaning.
• Updated README and LICENSE.
• New exception PIPError to handle pip errors.
• Main class renamed to Package.
• More verbose messages.
• Small code optimizations and improvements.