Add punycode support

Fixes #8

vendor/golang.org/x/text/language/common.go

@@ -0,0 +1,16 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package language
+
+// This file contains code common to the maketables.go and the package code.
+
+// langAliasType is the type of an alias in langAliasMap.
+type langAliasType int8
+
+const (
+	langDeprecated langAliasType = iota
+	langMacro
+	langLegacy
+
+	langAliasTypeUnknown langAliasType = -1
+)