Change Travis status to only show master branch status. (#865)
Change Travis status to only show master branch status. (#865)

So that pull request build failure does not impact project status.

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>
ii/coredns,johnbelamaric/coredns,johnbelamaric/coredns,miekg/coredns,miekg/coredns,ii/coredns,yongtang/coredns,chrisohaver/coredns,jremond/coredns,jremond/coredns,coredns/coredns