.travis.yml: bump Go versions and use '.x' to get latest patch versions
.travis.yml: bump Go versions and use '.x' to get latest patch versions

Change-Id: Ib536784b03c309592a8c046af6a62651310e7bc2
GitHub-Last-Rev: 24d3dd96324686f764ef7353864c14b8c08d598f
GitHub-Pull-Request: golang/gddo#589
Reviewed-on: https://go-review.googlesource.com/c/145239
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

golang/gddo,segmentio/gddo,golang/gddo,segmentio/gddo,golang/gddo,segmentio/gddo,golang/gddo,segmentio/gddo