Read the `(version-string, version-info)` from `added_value/version.py`.

def read_version():
    "Read the `(version-string, version-info)` from `added_value/version.py`."
    version_file = local_file('source', 'added_value', 'version.py')
    local_vars = {}
    with open(version_file) as handle:
        exec(handle.read(), {}, local_vars)  # pylint: disable=exec-used
    return local_vars['__version__']