Merge pull request #168 from golang/ci

Update the set of versions of go we test against.

Author: balshetzer

.travis.yml

@@ -1,21 +1,10 @@
 language: go
 
 go:
-  # this will flag backwards compatibility issues creeping in
-  - 1.6
-  - 1.6.x
-  # we intend to support only the latest version and perhaps the previous one
-  - 1.7
   - 1.7.x
-  - 1.8
   - 1.8.x
-  - 1.9
   - 1.9.x
-
-matrix:
-  allow_failures:
-    - go: 1.6
-    - go: 1.6.x
+  - 1.10.x
 
 script:
   - go build ./...