Move gomobile package to mobile

Makefile

@@ -1,2 +1,2 @@
 gomobile:
-	gomobile bind -target=ios -o txqr.framework
+	gomobile bind -target=ios -o txqr.framework github.com/divan/txqr/mobile

mobile/decode.go

@@ -0,0 +1,17 @@
+package txqr // package should have this name to work properly with gomobile
+
+import (
+	"github.com/divan/txqr/protocol"
+)
+
+// Decoder implements txqr wrapper around protocol decoder.
+type Decoder struct {
+	*protocol.Decoder
+}
+
+// NewDecoder creats new txqr decoder.
+func NewDecoder() *Decoder {
+	return &Decoder{
+		Decoder: protocol.NewDecoder(),
+	}
+}