travis: make sure to have latest tag
travis: make sure to have latest tag

The Win/Mac build scripts name the binaries using "git describe --tags",
so reproducibility requires git to find the latest tag.
By default, Travis uses depth=50.

vialectrum/vialectrum,wakiyamap/electrum-mona,spesmilo/electrum,pooler/electrum-ltc,vialectrum/vialectrum,fujicoin/electrum-fjc,wakiyamap/electrum-mona,neocogent/electrum,wakiyamap/electrum-mona,fujicoin/electrum-fjc,fujicoin/electrum-fjc,pooler/electrum-ltc,wakiyamap/electrum-mona,spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,neocogent/electrum,neocogent/electrum,vialectrum/vialectrum,spesmilo/electrum,spesmilo/electrum