[RFC/WIP] move tests and avoid packaging them

which installs the current codebase in a venv
and runs 'import git' to test if codebase can be
installed properly.
This adds virtualenv to the test requirements

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

and remove all previously used test related settings

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

by using exclude feature of find_packages.
py_modules are determined by new function, which
recursively scans the base dir but omits the
external modules.
Plus remove now obselete package_data setting

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

This should ensure that tests are NOT packaged into
release package by setuptools, as tests are development
only
+ fixtures after moving

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>