Update Go versions for Travis.
Update Go versions for Travis.

Also use Travis' container-based build infrastructure.

Stash-Crypto/btcd,hectorj/btcd,danoctavian/btcd,dajohi/btcd,cqswxj2013/btcd,btcsuite/btcd,pkothbauer/btcd,1d4Nf6/btcd,ltcsuite/ltcd,wallclockbuilder/btcd,CryptocurrencyCabal/htcd,runeaune/btcd,CryptocurrencyCabal/htcd,Stash-Crypto/btcd,toddfries/btcd,jcmincke/dcrd,qchain/btcd,btcsuite/btcd,BitGo/prova,mathiasrw/btcd,jongillham/btcd,soapboxsys/ombfullnode,btcsuitereleases/btcd,tb00/btcd,qchain/btcd,jimmysong/btcd,adiabat/btcd,stevenroose/btcd,ppcsuite/ppcd-old,BitGo/prova,jrick/btcd,jongillham/btcd,dajohi/btcd,Dirbaio/btcd,Cleawing/btcd,Roasbeef/btcd,1d4Nf6/btcd,jrick/dcrd,jrick/btcd,cjepson/btcd,cjepson/btcd,glv2/ppcd,jimmysong/btcd,aakselrod/btcd,toddfries/btcd,ppcsuite/ppcd-old,jcmincke/dcrd,Roasbeef/btcd,jrick/dcrd,dan-da/btcd,davecgh/btcd,soapboxsys/ombfullnode,pkothbauer/btcd,decred/dcrd,aakselrod/btcd,ppcsuite/ppcd,tb00/btcd,mathiasrw/btcd,DanielKrawisz/btcd,glv2/ppcd,ppcsuite/ppcd,dan-da/btcd,hectorj/btcd,btcsuitereleases/btcd,Cleawing/btcd,adiabat/btcd,decred/dcrd,danoctavian/btcd,runeaune/btcd,jcmincke/dcrd,Dirbaio/btcd,dajohi/btcd,cqswxj2013/btcd,DanielKrawisz/btcd,stevenroose/btcd,wallclockbuilder/btcd,jrick/btcd,ltcsuite/ltcd,Dirbaio/btcd,davecgh/btcd