add vendoring

vendor/gitlab.com/etke.cc/go/env/README.md

@@ -0,0 +1,13 @@
+# ENV
+
+Simple go environment variables reader, for env-based configs
+
+```go
+env.SetPrefix("app") // all env vars should start with APP_
+login := env.String("matrix.login", "none") // export APP_MATRIX_LOGIN=buscarron
+enabled := env.Bool("form.enabled") // export APP_FORM_ENABLED=1
+size := env.Int("cache.size", 1000) // export APP_CACHE_SIZE=500
+slice := env.Slice("form.fields") // export APP_FORM_FIELDS="one two three"
+```
+
+see more in godoc