refactor(resize): add Go version comment

resize_legacy.go

@@ -4,7 +4,7 @@ package bimg
 
 // Resize is used to transform a given image as byte buffer
 // with the passed options.
-// Used as proxy to resizer()
+// Used as proxy to resizer() only in Go <= 1.6 versions
 func Resize(buf []byte, o Options) ([]byte, error) {
   return resizer(buf, o)
 }