update to go version 1.10.3

.travis.yml

@@ -1,8 +1,6 @@
 language: go
 go:
-  - 1.6.3
-  - 1.7.3
-  - 1.8
+  - 1.10.3
 install:
   - export PATH=$PATH:$HOME/gopath/bin
   - go get -u github.com/opennota/check/cmd/structcheck