docs(license): add julienschmidt/httprouter license URL

path.go

@@ -1,7 +1,7 @@
 // Copyright 2013 Julien Schmidt. All rights reserved.
 // Based on the path package, Copyright 2009 The Go Authors.
 // Use of this source code is governed by a BSD-style license that can be found
-// in the LICENSE file.
+// at https://github.com/julienschmidt/httprouter/blob/master/LICENSE.
 
 package gin
 

path_test.go

@@ -1,7 +1,7 @@
 // Copyright 2013 Julien Schmidt. All rights reserved.
 // Based on the path package, Copyright 2009 The Go Authors.
 // Use of this source code is governed by a BSD-style license that can be found
-// in the LICENSE file.
+// at https://github.com/julienschmidt/httprouter/blob/master/LICENSE
 
 package gin
 

tree.go

@@ -1,6 +1,6 @@
 // Copyright 2013 Julien Schmidt. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be found
-// in the LICENSE file.
+// at https://github.com/julienschmidt/httprouter/blob/master/LICENSE
 
 package gin
 

tree_test.go

@@ -1,6 +1,6 @@
 // Copyright 2013 Julien Schmidt. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be found
-// in the LICENSE file.
+// at https://github.com/julienschmidt/httprouter/blob/master/LICENSE
 
 package gin