GAE fix for unsafe (#4)

* GAE fix for unsafe

Signed-off-by: Vishal Rana <vr@labstack.com>

* Forgot to return

Signed-off-by: Vishal Rana <vr@labstack.com>

unsafe.go

@@ -1,3 +1,5 @@
+// +build !appengine
+
 package fasttemplate
 
 import (

unsafe_gae.go

@@ -0,0 +1,11 @@
+// +build appengine
+
+package fasttemplate
+
+func unsafeBytes2String(b []byte) string {
+	return string(b)
+}
+
+func unsafeString2Bytes(s string) []byte {
+	return []byte(s)
+}