Implemented watching using filter package

* Added filters / watches
* Removed event dep

whisper/whisper_test.go

@@ -0,0 +1,47 @@
+package whisper
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestKeyManagement(t *testing.T) {
+	whisper := New()
+
+	key := whisper.NewIdentity()
+	if !whisper.HasIdentity(key) {
+		t.Error("expected whisper to have identify")
+	}
+}
+
+func TestEvent(t *testing.T) {
+	res := make(chan *Message, 1)
+	whisper := New()
+	id := whisper.NewIdentity()
+	whisper.Watch(Filter{
+		To: id,
+		Fn: func(msg *Message) {
+			res <- msg
+		},
+	})
+
+	msg := NewMessage([]byte(fmt.Sprintf("Hello world. This is whisper-go. Incase you're wondering; the time is %v", time.Now())))
+	envelope, err := msg.Seal(DefaultPow, Opts{
+		Ttl:  DefaultTtl,
+		From: id,
+		To:   &id.PublicKey,
+	})
+	if err != nil {
+		fmt.Println(err)
+		t.FailNow()
+	}
+
+	tick := time.NewTicker(time.Second)
+	whisper.postEvent(envelope)
+	select {
+	case <-res:
+	case <-tick.C:
+		t.Error("did not receive message")
+	}
+}