Fixed ical-go package include

vendor/github.com/laurent22/ical-go/lib.go

@@ -0,0 +1,18 @@
+package ical
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type strBuffer struct {
+	buffer bytes.Buffer
+}
+
+func (b *strBuffer) Write(format string, elem ...interface{}) {
+	b.buffer.WriteString(fmt.Sprintf(format, elem...))
+}
+
+func (b *strBuffer) String() string {
+	return b.buffer.String()
+}