'Reads the support-matrix.ini file and populates an instance
of the SupportMatrix class with all the data.
:returns: SupportMatrix instance'

def _load_support_matrix(self):

    if (sys.version_info >= (3, 2)):
        cfg = configparser.ConfigParser()
    else:
        cfg = configparser.SafeConfigParser()
    env = self.state.document.settings.env
    fname = self.arguments[0]
    (rel_fpath, fpath) = env.relfn2path(fname)
    with open(fpath) as fp:
        cfg.readfp(fp)
    env.note_dependency(rel_fpath)
    matrix = SupportMatrix()
    matrix.targets = self._get_targets(cfg)
    matrix.features = self._get_features(cfg, matrix.targets)
    return matrix
