Use Go1.11 module (#5743)

* Migrate to go modules

* make vendor

* Update mvdan.cc/xurls

* make vendor

* Update code.gitea.io/git

* make fmt-check

* Update github.com/go-sql-driver/mysql

* make vendor

vendor/github.com/jaytaylor/html2text/.travis.yml

@@ -0,0 +1,13 @@
+language: go
+go:
+  - tip
+  - 1.7
+  - 1.6
+  - 1.5
+  - 1.4
+  - 1.3
+  - 1.2
+notifications:
+  email:
+    on_success: change
+    on_failure: always