setup: fix distutils sdist for Vagrant

Allow distutils sdist to work correctly when using Vagrant + VirtualBox
shared folders, where hard links are not implemented.

See also: http://bugs.python.org/msg208792
salt: update oath-toolkit dep since Cython was added
salt: PPAs are for Ubuntu only, fix vim filetype
tests: check cyclomatic complexity
CONTRIBUTING: rewrite issue/pull request sections
Vagrant: switch to 64-bit VM

I'm not convinced that CFFI + liboath works consistently on 32-bit machines.