Adds the possessive s after a string.

    value = 'Hans' becomes Hans'
    and value = 'Susi' becomes Susi's

def append_s(value):
    """
    Adds the possessive s after a string.

    value = 'Hans' becomes Hans'
    and value = 'Susi' becomes Susi's

    """
    if value.endswith('s'):
        return u"{0}'".format(value)
    else:
        return u"{0}'s".format(value)