'__setitem__ should behave case-insensitively.'

def test_fixes_649(self):

    cid = CaseInsensitiveDict()
    cid['spam'] = 'oneval'
    cid['Spam'] = 'twoval'
    cid['sPAM'] = 'redval'
    cid['SPAM'] = 'blueval'
    assert (cid['spam'] == 'blueval')
    assert (cid['SPAM'] == 'blueval')
    assert (list(cid.keys()) == ['SPAM'])
