Switch Travis to Go 1.11

.travis.yml

@@ -7,7 +7,7 @@ addons:
 language: go
 go_import_path: "miniflux.app"
 go:
-  - "1.10"
+  - "1.11"
 before_install:
   - npm install -g jshint
   - go get -u github.com/golang/lint/golint