Use vendor when building (#201)

* Use vendor code for all go calls

* Add missing vendor dependencies

* Add travis_retry to yarn install

* Fix go test call

vendor/github.com/99designs/gqlgen/codegen/generate.go

@@ -0,0 +1,15 @@
+package codegen
+
+import (
+	"github.com/99designs/gqlgen/codegen/templates"
+)
+
+func GenerateCode(data *Data) error {
+	return templates.Render(templates.Options{
+		PackageName:     data.Config.Exec.Package,
+		Filename:        data.Config.Exec.Filename,
+		Data:            data,
+		RegionTags:      true,
+		GeneratedHeader: true,
+	})
+}