Signed-off-by: Jeffery To <jeffery.to@gmail.com>

This renames the Python 2 twisted package to python-twisted, and updates
dependents (i.e. obfsproxy) to reference the updated name.

This also fixes conflicts between the Python 2 and 3 packages. Twisted
installs some scripts to /usr/bin, and previously scripts for both
packages used the same names. This adds a "3" suffix to scripts
installed by python3-twisted.

This also adds python[3]-setuptools as a dependency, as the scripts
installed to /usr/bin depend on pkg_resources (part of setuptools).

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

There have been some new dependencies added in recent versions of
Twisted (mostly internal classes that have been spun out into their own
libraries):

* constantly (#5453), since 16.5.0
* incremental (#5454), since 16.5.0
* Automat (#5456), since 17.1.0
* hyperlink (#5455) since 17.5.0

Signed-off-by: Jeffery To <jeffery.to@gmail.com>