Update build status badge in README.md to SVG.
Update build status badge in README.md to SVG.

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