Master is now preferred on the first stitch

If the master is involved in the very first stitch it is now preferred (stitched first), making the global coordinate system the same as the master's coordinate system. Most applications will not care about that, but some might rely on the master being stitched first, for example because they start with content on the master only and don't want that content to change on the first stitch.
Fix #89

Added Connichiwa.onLoad() (or, alternatively, Connichiwa.on('load', ...)). Callbacks attached to this will fire on $(window).load() or immediatly when the window is already load. This can be important if we have common code: On the master, we want it to fire on $(window).load(), but since it is loaded via loadScript() on remotes, it will arrive AFTER the window has loaded, and therefore needs to fire immediately. Connichiwa.onLoad() takes care of that and should be preferred over $(window).load(), window.onload or body.onload.