upgrade travis to terraform version 0.7.0-rc2
upgrade travis to terraform version 0.7.0-rc2

version v0.7.0-rc3 has some problems right now.

bitium/mantl,mantl/mantl,sehqlr/mantl,mantl/mantl,bitium/mantl,CiscoCloud/mantl,CiscoCloud/microservices-infrastructure,CiscoCloud/mantl,CiscoCloud/microservices-infrastructure,datascienceinc/mantl,sehqlr/mantl,datascienceinc/mantl,KaGeN101/mantl,KaGeN101/mantl