travis: use other "coveralls" package
travis: use other "coveralls" package

see: https://github.com/z4r/python-coveralls/issues/74

pooler/electrum-ltc,spesmilo/electrum,wakiyamap/electrum-mona,wakiyamap/electrum-mona,spesmilo/electrum,wakiyamap/electrum-mona,pooler/electrum-ltc,pooler/electrum-ltc,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,wakiyamap/electrum-mona