WIP: travis changes (#2766)
WIP: travis changes (#2766)

* WIP: travis changes

Simplify Travis so it fails less often.

We don't need docker any more, let alone trusty and sudo, so simplifies
this, to just os: linux.

Signed-off-by: Miek Gieben <00b357f94cf3a1145a32703fb42e2d80418ab806@miek.nl>

* This?

Signed-off-by: Miek Gieben <00b357f94cf3a1145a32703fb42e2d80418ab806@miek.nl>

johnbelamaric/coredns,ii/coredns,chrisohaver/coredns,miekg/coredns,ii/coredns,yongtang/coredns,miekg/coredns,johnbelamaric/coredns,coredns/coredns