Add webpush-go dependency

# Conflicts:
#	go.sum

vendor/github.com/SherClockHolmes/webpush-go/README.md

@@ -0,0 +1,63 @@
+# webpush-go
+
+[![Go Report Card](https://goreportcard.com/badge/github.com/SherClockHolmes/webpush-go)](https://goreportcard.com/report/github.com/SherClockHolmes/webpush-go)
+[![GoDoc](https://godoc.org/github.com/SherClockHolmes/webpush-go?status.svg)](https://godoc.org/github.com/SherClockHolmes/webpush-go)
+
+Web Push API Encryption with VAPID support.
+
+```bash
+go get -u github.com/SherClockHolmes/webpush-go
+```
+
+## Example
+
+For a full example, refer to the code in the [example](example/) directory.
+
+```go
+package main
+
+import (
+	"encoding/json"
+
+	webpush "github.com/SherClockHolmes/webpush-go"
+)
+
+func main() {
+	// Decode subscription
+	s := &webpush.Subscription{}
+	json.Unmarshal([]byte("<YOUR_SUBSCRIPTION>"), s)
+
+	// Send Notification
+	resp, err := webpush.SendNotification([]byte("Test"), s, &webpush.Options{
+		Subscriber:      "example@example.com",
+		VAPIDPublicKey:  "<YOUR_VAPID_PUBLIC_KEY>",
+		VAPIDPrivateKey: "<YOUR_VAPID_PRIVATE_KEY>",
+		TTL:             30,
+	})
+	if err != nil {
+		// TODO: Handle error
+	}
+	defer resp.Body.Close()
+}
+```
+
+### Generating VAPID Keys
+
+Use the helper method `GenerateVAPIDKeys` to generate the VAPID key pair.
+
+```golang
+privateKey, publicKey, err := webpush.GenerateVAPIDKeys()
+if err != nil {
+	// TODO: Handle error
+}
+```
+
+## Development
+
+1. Install [Go 1.11+](https://golang.org/)
+2. `go mod vendor`
+3. `go test`
+
+#### For other language implementations visit:
+
+[WebPush Libs](https://github.com/web-push-libs)