Update Travis and snapcraft to Go 1.9.2

See #4064

Author: bep

.travis.yml

@@ -2,8 +2,8 @@ language: go
 sudo: required
 dist: precise
 go:
-  - 1.8.4
-  - 1.9.1
+  - 1.8.5
+  - 1.9.2
   - tip
 os:
   - linux

snapcraft.yaml

@@ -37,4 +37,4 @@ parts:
       strip --remove-section=.comment --remove-section=.note $SNAPCRAFT_PART_INSTALL/bin/hugo
     after: [go]
   go:
-    source-tag: go1.9.1
+    source-tag: go1.9.2