Update install instructions to include global deps
Update install instructions to include global deps

- knex-migrator and gulp are required
kevinansfield/Ghost,singular78/Ghost,cwonrails/Ghost,BlueHatbRit/Ghost,novaugust/Ghost,SkynetInc/steam,acburdine/Ghost,chevex/undoctrinate,dbalders/Ghost,stridespace/Ghost,vainglori0us/urban-fortnight,cwonrails/Ghost,stridespace/Ghost,dbalders/Ghost,bitjson/Ghost,Kikobeats/Ghost,leninhasda/Ghost,sebgie/Ghost,letsjustfixit/Ghost,Gargol/Ghost,Kikobeats/Ghost,ErisDS/Ghost,e10/Ghost,janvt/Ghost,mohanambati/Ghost,acburdine/Ghost,TryGhost/Ghost,JohnONolan/Ghost,JohnONolan/Ghost,kevinansfield/Ghost,leninhasda/Ghost,stridespace/Ghost,dbalders/Ghost,TryGhost/Ghost,e10/Ghost,Kikobeats/Ghost,acburdine/Ghost,novaugust/Ghost,mohanambati/Ghost,letsjustfixit/Ghost,SkynetInc/steam,kevinansfield/Ghost,vainglori0us/urban-fortnight,BlueHatbRit/Ghost,sebgie/Ghost,ErisDS/Ghost,ErisDS/Ghost,letsjustfixit/Ghost,sebgie/Ghost,bitjson/Ghost,TryGhost/Ghost,novaugust/Ghost,singular78/Ghost,mohanambati/Ghost,singular78/Ghost,cwonrails/Ghost,janvt/Ghost,JohnONolan/Ghost,vainglori0us/urban-fortnight,Gargol/Ghost