Bugfix (regression): No redirect if displaying a bit later

Because of the first condition in `display` (introduced in df56c1908222809a0587699610b931ac3d69136c) the page would redirect (location.href = url).
[Minor] Reorder functions’ place in source code by their “categories”
Add option to set a delay before preloading kicks in.

To use: InstantClick.init(<delay in ms>)
Or, with blacklist mode: InstantClick.init(true, <delay in ms>)
(The order of InstantClick.init’s arguments doesn’t matter)